We have been experimenting with support for impure builders and have some prototypes, we’re excited to showcase these soon. These are of course just prototypes at this stage and we cannot commit to any guarantees about them being supported ( I hope they do though ).
As for integration with lang2nix tools like dream2nix, floco, node2nix, etc - it is currently possible to use these with flox but we currently lack “proper integration”. We’re working on a cleaner interface for using “regular” nix flakes and expressions with flox which will hopefully make this usage easier. For now I do have an example of using floco ( a lang2nix tool ) with flox in this thread which you may find useful: Install nodejs package to env - #4 by aameen