This post hits me deep in the core. I spent a around 2k usd on custom features for my game that I thought were essential to make my game unique and stand out. Looking back I really regret doing this and do not suggest it for people who are not efficient programmers. That is unless you have a big budget which I'm assuming most do not have.
When the big intersect update came out that fixed a bunch of stability and vulnerability issues I knew I had to upgrade if I ever wanted to release my game. There is no easy one click way of upgrading major releases like this. This left me with two options, try to migrate everything or start over. I obviously didn't want to start over so I went the route of hiring someone to migrate my features. The programmer got close to fixing most things but the whole process was convoluted and painful. Some features where never truly debugged which was mostly my fault because I failed to stay in contact with the coder. I also knew that I would end up crossing the same path again one day soon and couldn't stomache the thought of it lol.
My suggestion is if you can't program to try and base your game idea around the current features of the stable engine. Just work long and hard on your minimal viable product. The core that makes your game your game. Worry about the fine details when your close to a real legitimate release. I say this because you could be working on your game for 2-3 more years before a real release is possible. In this time the engine could go through some huge rewrites and your plans could be spoiled multiple times.
Also if you don't have a programmer on your team it's probably best that you focus more on the talents you are bringing to your game. This could be art, music, story telling ECT. Take it from someone who has restarted his game like 4 times. Just forget about custom features until much later in your games development. Build an audience, get some eyes on your game so you can justify spending some money on it. Also note that if you can't fix a bug within a custom feature yourself, it may never be fixed.