Xeviat
Dungeon Mistress, she/her
Personally, I was in the some boat once (port the best ideas from 5e into 4e), but I found it easier for me and our group to go the other way and pull our favorite parts for 4e into 5e.
Which parts did you do? I did consider sitting down and writing an "Advanced Monster Manual", and then making a variant feat system so you get feats and ASIs. Since it would be compatible with 5E, it might get more use.