Deadpool has a big enough cast of characters to work around the Marvel Universe. I mean theres a few characters that belong in DP more than anyone else. Taskmaster for 1. Hes probably the only person with the possibility of being in another movie but should be in a DP movie. His run ins with Syrin and Juggie should just be ignored. Cable's origin could take up an entire movie and time travel can get annoying. I would be completely ok with them skipping over him too.
You've got: Taskmaster, Agent X, Outlaw, Sandi, Weasal, Zoe and the others from Landau, Luckman, and Lake, Bob, Blind Al, Fenway, C.B., Patch, Sluggo, Slayback, Copycat, T-Ray, Irene Merryweather, The Cat, Black Swan, and all the mobsters from Taskmaster and Agency X titles.