As someone who has definitely struggled with face limits while mapping (seriously, one does not simply chop 5000 brushsides from an existing map), I know how this feels.
But I think a solution you guys should consider is using Propper. This wonderful tool allowed me to take some of the higher polygon brushes I had in my own map and convert them straight into models. You know that bridge over the electric pool in On a Rail? That was entirely brush based. I turned that into a propper_model, ran Propper, and then placed a model there in it’s place. Easy way to save about 1000 brushsides.
I’ve made it a practice to keep copies of everything I converted with Propper into a separate vmf, just incase I need to edit/recompile. It makes the whole process very easy in my opinion.