My personal list of wishes:
1) Missions from WWP and W2
2) Mission editor from WWPR
3) Ability to place mines and worm spawn points in the in-game map editor
4) Adding Wormnat2, wkTerrainSync, wkRealTime, wkJellyWorm, wkPin as the default part of the game
5) Hats. And also ability to create your own like in Worms WMD
6) Adding all additional soundbanks from different WWP versions as the default part of the game
7) Steam Workshop for uploading maps, missions, graves, flags, terrains, hats, fanfares and soundbanks
8 ) Project X features
9) Weapon editor from W2
10) Adding 2 additional music tracks from WWP and all music tracks from W2 as the default part of the game
11) The Forts game mode from WWP
12) All features from the upcoming Anniversary Edition
13) Cross platform multiplayer, which allows to play together the players on all platforms, including also PC
14) Ability to invite friends to lobby directly via Steam
15) Ability to preview lobbies in Wormnet (see which players are in there without need to join a lobby)
16) The Buildings feature from Worms WMD
17) Ability to draw maps with maximum available dimensions in the in-game map editor
18) Ability to choose water color in the in-game map editor
19) Ability to create custom animated graves
20) Full color support which allows to create maps, graves, flags and terrains without messing with indexed color
21) TUS integration
22) Adding all missing Wormnet flags
23) Ability to directly convert replays to video files fully and partially of the replay's length
24) Adding playback control line for replays
25) Ability to change or hide Wormnet flag in the game
26) Adding a snooper to the main files folder as the default part of the game
27) Ability to change controls in the game's settings
28) Support for all text characters
29) Features and contents from Online Worms and WWP Aqua
30) Ability to create custom terrains with non primitive background, which would allow to put something much more complex (and maybe even animated) instead of just repeated small image line with gradient
I listed everything I remember for now, might add more in the future. Most likely many of them already have been listed above by others.