Let's remember how Nostalgia became a proven template. Vic included it earlier in castle tournaments, but it wasn't played much there. As a result, he included it in the IP, where fans of HLek, when playing as Cherk, had to play against it. (It seems someone was unhappy that he put it in instead of the proven Spider.) As a result, Nostalgia was tested and it worked out.
Why not try to find (or modify existing) other good templates? And where else to do it if not in tournaments? No one tests them seriously otherwise.

We need to ask the experienced players how to specifically change 8x12 and 8mm6 to make them more playable.
A variant of changes was proposed. Download the template and specifically list what is wrong with it. While the tournament hasn't started, the organizer is ready to change the templates.

There are a few important points in your story. First, Vic also included 8x12 in his tournaments at first – it didn't work for anyone at all. While Nostalgia wasn't particularly refined before or after the tournaments, it simply turned out to be more playable in HotA than the SoD version (whereas 8x12 was the opposite). And I have doubts that it will be so easy to make it playable just by tweaking a couple of mandatory and non-mandatory paths.
Regarding Might and Magic 6, I didn't even try to play it in HotA, but I don't think it differs much from the SoD version. And the main problem with Might and Magic 6 (at least in SoD) is the too linear encounter in the "center" at the end of the 1st, beginning of the 2nd week. And then, very often, the one who got more power along the way immediately pushes the other into a corner, and then the whole question is whether there will be air control in the corner so that they can break through to new zones, bypassing the opponent.