Larger islands in general, more area for PvP. Put smaller Team SkyWars maps in Solo too. Put a kill counter into the scoreboard; Team SkyWars do "{your_kills} ({team_kills})" and also show the selected kit in the scoreboard.
Rework of following maps to make PvP easier on them and making them look more professional:
Flowers, Scare, Temple, Trees, Bones (Bone blocks guys, bone blocks), End, Castle, Nether
Add SkyWars maps in the style of Lucky Island maps. They're a lot better to PvP on.
Remove Tron entirely since that map is just annoying and bad for PvP.
Add vertical knockback when getting hit in air with snowballs and eggs so some satisfying air hit combos are possible when knocking someone off an island. (Look up SkyWars air hits on YouTube)
Probably cobwebs and throwable heal 1 pots (single, stack of 2, stack of 3) in the chest loot.
Nerf saturation healing.
New map style: reversed maps in Solo; that means everyone will spawn circular like in SG in the center of the map on a circular island with a big ring outside them which has the chests with the better loot on it.
Example:
Maps with one or two closed rings as the mid island, big center island and the islands on the outside are the player spawns.
Example:
Maps which have the spawns connected with the center (+ a ring outside).
Example: