Slimmed down version is a great idea actually !So, I was able to do a few tests and it appears that much has changed in A20, that breaks RAT and BCM (mod required for RAT), a large part of that is the change to how the player IDs are sent across, the format of that has changed.
In order to make RAT work again, it would require significant work to update RAT, and the work to update BCM, I'm not even sure where to begin with it (due to my own limited abilities, not BCM).
That being said, while RAT still connects to your game server and some things work, there are many things that aren't going to work. Such as getting blocks, items, etc. Various events like player inventory, horde spawners, etc. There's a lot.
But there is also a lot that does still work, or would still work with some updates. As some of you know, I had been working on an entirely new update for RAT, RAT3. I started all of that work without using BCM, so that code still functions. Currently that is mostly things like the actual server management for local servers. So start up, shut down, serverconfig.xml changes, chat, Discord, etc. All of that works (again with some modification).
If there is interest, I might consider slimming RAT down to the things that don't require BCM and seeing what I can do with that, since the RAT3 code was never released and seemed to work pretty nicely.
But, as it stands, the current release of RAT, the majority of functionality does NOT work with A20.
So if you're interested in a slimmed down version of RAT (I'll try and be more specific with what features would remain at a later date), please let me know. Either by replying to this post, contact me in Discord, post in our Discord, etc.
I can't be more honest in that your interest is directly related to how much time I spend on this (if any), going forward.
I might miss the grab bags and teleportation and duke exchanges and the various chat and macro stuff, but ":"meh". 95% of the time use it for the basics anyways !