Hm... Looking over Tob's new sheet, I can understand the reason for most of those Megas. As he has a regular Mega and an "unstabilized" Mega as a kind of Dark Digivolution version. Or at least, that's what I get out of it. So two for the standard Mega and two for Royal Knight (Gallantmon and ChaosGallantmon). However, I do feel like only one Ascended Knight form is necessary. If this were a Digimon that was supposed to be the leader of the Knights, I wouldn't mind him having a second Ascension that's more powerful than the first. In this case, though, I would personally prefer it if there was either Gallantmon Crimson Mode or MedievalGallantmon, but not both.

So basically, while there would be six Megas at that point, the reason for it would be that only three tiers just like Omnimon, but with two on the tier. But one of each Mega form would be her "True" form for that line. The others are kind of...corrupted versions of Digivolution akin to SkullGreymon in the Adventure series? Where they technically exist and can potentially happen, but it's not the form they want to take. Like how the main group in Adventure had Greymon Digivolve to SkullGreymon. They never wanted to use it again, and ever since, only used MetalGreymon. Do I have that right, Tob? Is that more or less what you're going for? If so, I would be okay with this. I've used a similar system in the past (where my Agumon character could do a branch Digivolution into either the Greymon or GeoGreymon line). If not...well, I would agree with RBY. Being able to freely use them with few disadvantages would be a bit of overkill, even in the endgame.

(Out of personal preference, I think that Megidramon is a good idea. It just really depends on how it's implemented into the story when it comes.)