lol, 
I remember when I first started using UE4 the UI felt a bit odd to me (funny considering I’m a blender user) but it quickly grew on me and now it feels like a warm snuggly blanket
Having said that, I really like the dark theme you’ve done, it feels really clean and tidy. The light theme is waaaay too bright for me though (also funny given that I use light theme in VS).
My 2 cents is that anyone who designs any sort of theme is going find the herd instantly divided into people who love it like a kitten and people who hate the changes with the fiery heat of a thousand suns.
I highly recommend that you make it in such a way that you can turn it on or off with the flick of a switch so that people can take it or leave it with little more than a click.
The other thing you might consider is making your theme in such a way that allows other people use it to make their own custom themes…