Cauldron is a basically a server that can run Bukkit and Spigot Plugins with mods from Forge, Plus, This can be a option for people who want this for modpacks,
Sponge is also similar to Cauldron, Except Sponge runs code different from Bukkit and Spigot.
WorldEdit + Serverside mod setups for Forge (Perms and etc.) is a plugin, But why not the Forge version as well? There's a Forge mod for WorldEdit and Sponge doesn't have WorldEdit, And Sponge is planning to implement WorldGuard with the creator of WorldEdit/WorldGuard, while there has been many different world guard plugins for Sponge like FoxGuard. If in fact you only plan to add Sponge Support later.
Also, I want to have Squake if I plan to add a bunnyhop gamemode to my server, Because Bunnyhop is one of my favorite gamemodes and will be based with the Parkour Plugin.
Flan's Mod is one of my favorites, but I rather have it with the mods and Flan's Mod Content Packs themself.
Also, It should be allowed that the server can choose a older version for a older version of Minecraft.
I will accept one of the following:
The Cauldron/Sponge support: (Cauldron backups that want to be downloaded can be easily found in Google "Cauldron Minecraft Server") (Sponge: SpongeVanilla and SpongeForge)
All of them
Either FTP support and allow custom server jars
WorldEdit and Forge Essentials (+etc.)
(btw, would be nice to have Enjin/DonationCraft and Votifier (+GAListener)