Agreed a summoning ability would be pretty cool. I honestly feel like there's so much more combat mechanic possibility, and even static summons (something that stands still and shoots, or heals, etc.)I came up with a couple of new things that I would change or add to the game.
1) Necro and druid ability to summon creatures.
The druids of the spirits and the neсromancers are itself undead.
(a good mechanic would be if necr would raise only those who were killed nearby with a chance = x (the chance depends individually on the mob). Of any mobs (archer archers from a tank tank, etc., but of course with modified textures and effects) except world bosses and players)
Since this game used a lot of the old UO stuff, I agree they should go with a summoning skill. Also a bard class would be cool. One fun thing about UO was having a high level bard provoke mobs to fight each other. Would love to be able to do that here. They would have to be limited to not be able to do any other damage, otherwise they would be super OP.