idk, but I figure anything up to High E6 and 3rd level spells, can be smushed in.
The only consideration being "when", or how long it takes for stuff roll in.
I'm thinking Homebrew-for-now Psi might fit on the Warlock, especially with it's recharging Slots bit.
Heck some things are almost the same as 3e.
And Hello new 5e Board.