I was ready for a few more turns only to try out some end game mojo but... that said I'll concede to the Ermor/Ag Axis. So you two aren't going to duke it out?
Under "Shoulda, coulda,woulda..."
Should have done many more Plagues. I learned too late the potential of that spell. I think it could have been quite annoying even for Chaliced Ermor (Chalice can't be everywhere

)
Should have amassed more ponietroopers and launched them all at once (as Sax suggested) instead of piecemeal. I did have significant stealthy forces sneaking towards Ag that would have had Dark pulling out some hair.
Should have saved death gems and cast a D12 well of misery with the Crone. Would be tough to dispel.
Could have protected my twiceborn crone MUCH better and used her more effectively. Wish I had bought enough Astral/Blood for critical mass (barely started blood economy a few turns back).
Eriu temples are only 200gp. Tried to leverage an immortal/twiceborn strategy with that. My Dominion almost suffocated Aby by accident.
I enjoyed my alliances with Aby and Man very much. They were true to their swords. We should have started working closely much sooner (all three of us vs a single smaller opponent early/mid game, then another..., then another..)
Ag's second generation marble dudes were very tough cookies. Nice recovery Dark after the lightning incident on prototype #1.
Thanks also to my enemies. Without them the game would be nothing.
-SSJ