Map size and Rev length: Instead of a 7k x 7k map from the beginning, maybe we can try starting with a very small map size, such as 2k x 2k, and every 1 to 8 weeks (or perhaps whenever it is determined that the current map is or will soon become too crowded, or there is a desire for more of one or more biomes that are currently in short supply) we expand the map by 2k in each of the two horizontal directions. The map continues expanding until a new version of Minecraft gets released (and we determine that we are able to update to it), or perhaps until travel across the map is deemed impractical (which we would have to define as some amount of time that is required to travel that distance), or until the map file is deemed too big.
Spawn: A simple spawn that is easy to navigate and treats all directions of travel at least roughly equally would be best. Perhaps players can walk through the list of rules and information, then take a water drop/elevator down to a central area with roads coming out of it in similar fashion to rev 22. The spawn nether portal could be down a set of stairs directly below this central area. I am also not opposed to a hotel-style spawn (similar to rev 20), provided it is still easy to navigate and treats all directions at least roughly equally.
Nether portals: How about we stop making nether portals something that only a few people/cities get their hands on, and start allowing anybody to place a nether portal. If you are worried about grief, could we not just make an unlit nether portal somewhere, and then modreq to have it lit (surely we can trust the mods/admins, or perhaps LogBlock, to determine if the nether portal will cause grief in the other dimension (remember: distances in the nether and the overworld correlate via a simple ratio, and whether or not two portals in one dimension lead to the same portal in the other dimension is determined by how closely they are spaced, and should be predictable in advance via calculation (and perhaps observation, with mod/admin assistance if need be)).
Terrain generation: I am not certain whether or not non-vanilla terrain gen is beneficial in the overworld, but if we decide it is, lets at least make it so that biomes match with the stuff inside them. For example, if F3 tells me that I am in a plains biome, then I should not see an overabundance of naturally-generated trees. If F3 tells me that I am in a (regular) forest biome, then I should not expect to see jungle trees (unless I am in a transition zone between a jungle biome and a regular forest biome). On the other hand, if we determine that a whole biome is necessary to make more abundant, then we can change a biome (or a portion of a biome, in the case of something like an ocean biome), and make sure that it shows up as that new biome in F3, and also has only the features that could have been in that biome had it been naturally generated.
Events: My favorite event, so far, was Super Mini Games. I think the time for the events are good, though I am not opposed to them being an hour earlier. What I hope does not happen, is that they start later than when they start, now.