I'm bored enough to want to try and create 5ed versions of my 4th ed D&D group. The problem is really transferring over some of the abilities we have into 5e.
The Warlock is currently a Great Old One warlock, however in 5e that would give him telepathy, which he currently doesn't have.
The monk does have telepathy (racial) and his shtick is having really high passive perception/perception in general.
We also have a changling bard... and I still haven't properly figured out how to do swordmage change over yet.
Well, the one thing that would be nice for the bard is that she'd get her languages back. Some o fthem.
Warlock would lose his ability to speak every language.