For PvP, I'm assuming a Coliseum type feature is on its way - 15 v 15 (3 rounds of 5v5).
For PvE, I'd love to see more guild stuff. Big like Raid style bosses that the whole guild has to pitch in for.
Another PvE idea would be an endless level or endless waves style thing where you just see how long your heroes can last.
Double influence and double guild war rewards would be interesting.
Guild Wall style thing to help coordinate.
I think I'm mostly fine with how it is now. I've seen some folks request something related to talking in guild chat or global/vip and I absolutely hate that idea. I don't want to see more spam in global/vip and I certainly don't want guild chat, which we do use to help coordinate GW, gummed up with people saying "12345 daily quest."
Well, trying to think of the things that aren't already represented there ... (and part of me hesitates to suggest this as I doubt I'll ever be high enough to take advantage ...) you could add a +50% or +100% influence perk.
Soul chest from DS is also missing, but that hasn't aged well ... probably due to ownership, tbh.
Is there a VIP perk for increased tokens from GW? How about increased drop rate of stones in Elite? Increased drop rate of gear in Normal? Free refreshes of merchants? Extra free daily stam (eg. a 4th one at like 9 am)? Faster energy regen?