I'm unsure of how I like this trend of creating theorymon to counter the meta moreso than improve the mons with thematic and sensible additions.
Overall this slate is interesting having a bunch of slow mons and giving them cool things but I feel there needs to be some sort of discussion on the nominations having thematic and sensible boundaries before we see stuff like Flash Fire Forretress or something like that because I think Regirock and even Miltank's changes are pushing it to an extent.
The thing is, the aim of the project is to give these mons viability in OU, which given the saturatedness of the tier, implies giving them a niche, which normally implies making it check/counter something or other in the meta, or being able to break through something or other in the meta.
We don't just add theorymon willy-nilly, and during the discussion process we explain what the aim of each one is. This is why you see less defensive submissions, as most people like to make something more destructive, rather than find a new way to counter a major threat in the meta.
A lot of the suggestions will receive a "What does it do?" question before being accepted, and aren't generally accepted if there isn't a suitable answer.
I can accept that Regi was pretty sketchy on the flavor side, but Fairy = mythical = legendary maybe, (seriously grasping at straws here), and this was outweighed by what it could do - Counter both zards (well, standard sets at least) without being a Mega. This was the concept behind it, and its SO hard to do without buffing something extreme like Sand Stream Diancie (which would buff the mega as well).
In this case, without the Fairy typing, it would be 2HKO'd by X's Outrage or Y's Focus Blast.
Saying that, we do also have common sense, and Flash Fire Forretress (or Levitate Jolteon) or something that goes that way to being non-sensical is gonna get rejected. Flavor is something that is desired, but is not essential as long as its not too ridiculous.
The slates will sometimes have some sketchy flavor, but they should always give something new or interesting to OU.