Thats not too hard to model.
Just let fighters defend SBRs.
We’ll already made production capacity more realistic but limiting IPCs spent at an IC rather than no. of units.
So maybe SBR should destroy IPCs as well as reduce production capacitiy.
Actually, what if we purchase at the END of your turn, and pick which ICs to build them with. At the beginning of your turn some of the units may be destroyed while building and you never got to use them. :-D Thats pretty cool on the timeline.