All that stuff has already been suggested, I'm more interested in the story bits (either custom or original which was kept) which people would like to be different.
hmmm, story bits eh? you could maybe add other options to diplomatic/subversion/domination paths for each kingdom/empire/theocracy/etc. maybe with the consequences of how much time each plans eat up, how much fame and/or infamy ainz gains and similar such good and bad consequences. and how if plans are abandoned half way due to specific events what those results are. (like sorcerer kingdom announcement happening earlier than planned, PDL showing up, other dragon lords actually getting off their asses.)
for shits and giggles example, imagine if juvnic's empire was handled with greater subversion instead of mostly diplomatic, like how the re-estize kingdom was handled before the domination switch got flipped. i could think it'd be a rather amusing scenario if we turned juvnic into a alex jones type where his paranoia actually pays off and he steadily creates and anti-ainz alliance.
personally i think you could have a lot of fun with that premise if you decided to make more custom story choices or canon-ish story approaches and explored the pros and cons.
alternatively, since ainz is quite different from get go. how about instead of JUST playing adventurer by himself and his wifuable companion, how about his also sending out two other naz teams for info gathering purposes? and this snowballing into some different versions of how the shalchair/elder dragon mind control event and likely other custom events play out? this should give naz some quicker info on the surrounding kingdoms and could introduce the theocracy and elves sooner.
also we have no idea if someone can be revived after being killed by wild magic. i'm thinking specifically by corpse dragon lord. could be interesting to have that explored if ainz made too many fuck up choices and wasn't cautious enough with world item distribution.
any of these ideas helpful winter?
also on a personal note i like the initial choice with PDL's offer in the game, but slightly disliked the result being the same regardless. and no consequences good or bad from the choice. i mean i get why, it's end game at that point and having ainz accend to godhood was his plan. but more choices like those with actual good/bad/and gray area consequences are what i'd like more of!
game play elements eh? maybe RPG like mechanics added to when ainz is fooling around as an adventurer? dating sims mechanics applied to non-naz characters? similar but different dating sims mechanics applied to nazz characters that operate off something like a loyalty loss system (maybe with it being all/mostly in ainz's head and why he opts the fake it till you make it method)? another idea could be the nazz loyalty loss system bleeding into ainz's sanity and stress. possibly with the idea of X event with albedo, keno/evileye, or whatever 'main wife' the player has chosen could break the loyalty/sanity system. or just replace it with whatever more realisitc stats instead of ainz's overthinking. (yes this would make ainz more like juvnic. but in some ways it could really fit early-mid game if we're talking only the remake.)
