You cannot determine if it's any secret relations because the time gap before his death, during his death and his revival is not exactly in close ties due to the issue leading to over 60 reasons. That reason you placed up there is one of them. Now there are 59 other reasons with different outcomes and that one you placed just happens to be one created out of sheer thought due to either tag relations or family connection. (Which they don't have family connections unless it's "mentioned" otherwise. But since it's not mentioned at all, it's only normal speculation and not a strong one.) The red aura is merely the glove activity of it's usage. Now remove the glove, where is the aura. There is a habit here to where things visually automatically draws people into thinking it's automatically connected to someone. Apparently she has a mysterious power without the glove but yet people think the red aura automatically connects to Raidou. She has a copy cat glove equipment that copies techniques. Her mysterious power likely comes with the feedback that she can possibly keep them all as a bonus after stealing them. At this point, who knows. But who am I kidding? I don't even think it's a glove concept anymore granted that there are outfits to where she is not using it..so this concept is out of the window as there are more possibilities. Either she received a sample of Raidou's DNA to have the ability to use other moves? or maybe you were fortunate to be correct that she is related to Ayane or Raidou. (Which seems unlikely unless TN wants to say that they are related to provide even more confusion to the viewers for no reason.)
First of all, about the red aura, you already answered to it from yourself: you can see it even in the outfits where the glove doesn't appear. I don't think that this can be a so big mistake from TN, on the opposite this should be the evidence that the glove is not the cause of the power.
About the rest of things, what I said is indeed speculation but is based on more things that alone usually doesn't make a coincidence, and on the fact that DoA usually uses simple background stories for his characters (the most complex things are maybe the vicessitudes of Hayate and Kasumi between the first and second tournament).
- TN gave to Honoka a connection with both Raidou and Ayane. Yes, even Marie Rose, but while the affinity between Honoka and Marie it's simple to see thinking that both of them are intended represent moe characters, the choice to join her with Raidou and Ayane that are of a complete different world - the shinobi one - appear truly strange.
- Honoka's victory line with Raidou's tag assumes that in the past she has already seen Raidou somewhere, that sentence in fiction is always used for similar cases (but of course the reason for it could be for any kind of, not necessarily a father-daughter relationship). Raidou in Tag with Honoka has very strange behaviors, in the opening say to be kinda of scared, in the ending refuses to talk to Honoka's question. In both the circumstances it's the first time that the character give more the feeling to be goofy rather than scareful (just like the clichè of an scareful father that lose completely these characteristics in presence of the loved daughter for example, a meme already used in DoA for Bass with Tina). But this could be even a wrong impression of mine. Also, we have to remember that Raidou currently has no memories of his past, so if also this was the case, this should be only an hint of future story developments of DoA6 (just like the alliance between Kasumi and Phase in tag, just now not canon).
- Then there is what it's always said all the times: Honoka has a power similar to Raidou for both skills (copy) and appearence (a mini red aura). Honoka has an appearence similar to Ayane for hair and eyes. Again, this can mean anything, but seems surely hint that the DNA of Raidou is in some way owned from her.
In my opinion the scenario that explain all of this adding less speculation possible to the infos that were already got -
so not the only scenario that can explain it, but I repeat what explain it having to make imagine you the less development possible for connecting the dots - is that Raidou got a children, lived with some few time with her because she could keep some very vague memory of it. You say that something similar is against what we know of Raidou - an evil character that hardly we could imagine with a family - but if you think about it's already far from what we know of him to see this side of Raidou in DoA5LR, put in tag with a nice Japanese schoogirl and with a relationship that is surely not presented as twisted or evil.
I really think that Honoka in future will be used for showing a good side of Raidou not seen before, and that in the end the character could get a redemption from his status of evil character just through her (exactly as I think that to see Kasumi and Phase in Tag foreshadow the turning to the Shinobi side for the clone). But again, like I already repeated endless times, so far this remains only speculation =)
3) Again, there are no substantial mention at all. The speculation is only of normal base because the theory behind this suggest that Raidou once again falls prey to abusing another woman for his old selfish desires which he may no longer had around that time to even begin with. Throwing in Honoka within that particular timeline is completely off. Raidou was pure evil. His greed caused him to seek power after the events with Burai as well as after Ayame.
4) Honoka may have a grandmother with no connectivity at all for all we know. She is a highschool student that may have grasped a device for her powers or something kawaii to throw viewers off the hook. I don't see how it's...unknown...for a grandmother to take care of her grandchildren, It's only normal since it's her grandmother. Also Raidou's body was taken by Donovan after his collapse. The situation previous to this is that in past he was willing to give himself up for higher power for Donovan's experimentation but yet would only do it for his own purposes and likely may even betray Donovan in the end if such a outcome arisen. You see, "now" it was a good time for Donovan because he wiped his memories to prevent such things from happening. At this point, there are many reasons so who knows.
3) Indeed there is no mention at all of what I said, my point was just to say you that a such timeline is theoretically possible - getting into account only the objective facts, not the intentions of the charas - contrarily to what you seemed to state (if I didn't misunderstood your previous post). Also I repeat that I wasn't suggesting that Raidou abused another woman, this time the thing could have been consentient imo (it's actually the more likely scenario
if Honoka is really the daughter of Raidou: it's unlikely that TN could show her without hard feelings toward him - as their calm tag team already do - if Raidou would have hurted her mother).
4) I think that you misunderstood me: my point wasn't that is strange for a grandmother to take care of her grandchildren, the point is that is strange that to do it are not her parents. I believe that TN used that line for Honoka's background not because the grandmother will be revealed to be an important character in future (we could also not see her at all), on the opposite because their point was to make question to the people what is the reason because Honoka didn't live with her parents. There are of course many possible explanations for it (not only that Raidou is her fater, for example both of them may have been died for any reason), but the point is anyway that TN setted purposefully a mistery behind Honoka's paste, whatever can be the fate of their parents.