I have not gotten back to attempting huge maps since V1.21 was released. With V1.17 and prior releases, huge maps were the closest thing to infinite crippled corruption and tedium that I have ever seen.
I would think that a GOTM on a huge map would need some sort of accelerator or modification to make it even practical in this lifetime. If "Tournament Scoring" were functional and in place, then it would be possible to record a score for the games after some conditions were met, but without having to spend 6 weeks playing out the game to a known result.
I would personally like to see some tiny and small game sets that have crafted maps to test specific game play conditions. This would mean that relying on randomly generated maps that have not had a QC inspection review would be out of the question.
Most people would need a couple of small map games to fill the time space of a standard game.
An example of a cool set of maps to make up a tiny map game set for the GOTM, would be to have a preset order of play for three tiny maps where the there are the same 5 civs on each of the maps. The terrain layout of the maps would be a secret, so you would not be sure of how things were arranged. The three maps could include:
1) an edited version of galley accessible separate starting land masses and islands (I would definately modify longbowmen or explorers to be a weak Marine on this map),
2) a chokepoint and rough terrain pangea with off continent bonus land masses.
3) an open pangea
4) a caravel accessible two major continent plus islands map.
5) a cram packed map with the same 5 base civs plus 3 or 4 more (talk about your get tough early or die scenario, yeeha!!)
Because naval warfare is so much of an after thought, I definately think the focus should hold GOTMs to very low water percentages.
More important than map size manipulation on large and huge maps would be some creative land mass manipulation. I personally would hate to see more large maps until we have explored some creative game challenge permutation on standard sized maps and smaller.
I also would vote for never, ever having Huge maps as a GOTM because the level of tedium and time commitment would border on the psychotic. Except for GOTM's I rarely ever play a game to completion using the standard rules, the outcome is almost always determined much earlier in the process.