Hey all, just registered because I just noticed this blog post. I am a game developer for 15ish years, 3d technical artist as a fulltime job, and hobby developer. I played Drox primarily from your games (I tried a bit of the others too, but played Drox mostly). I use Unity in both work, and at home (this is not an Unity ad, I fully believe Unreal is capable of all of these too).
I strongly suggest switching, as it is not an issue to build a random world in Unity, or use pathfinding in a dynamic world. The learning curve isn't too steep too if you are used to game making engines. The asset store is full of useful stuff that you might need, from particle and sound effects to pathfinding solutions to monster collections (though using store assets in the final product is a bit cheap, but excellent to learning/modify). There are a lot of online courses, paid and free too, that handle game development in Unity (I used Pluralsight when I needed it, it is paid but very focused).
All in all, you should really try to mock up something in Unity in a few days and see how it goes. I fully believe a game like Drox could be done in Unity without major problems.
Anyways, thanks for reading this through, it is not a paid ad or something, I just wanted to write it because Unity was a really fresh experience to me after all the inhouse engines we had to use.
Best luck for your projects!