I understand the limititation, anyway let me theorize a bit anyway ;)
If i understand you correctly, the problem is in regards to have the complete action stack for step-wise undo possibility, right?
Me personally, I use source versioning for the possibility to undo changes - in my case, git - and to be honest, undoing changes etc. is so much quicker just reverting the changes or going back to the usual safety commit before the changes happend, as every changing action directly in the editor triggers all these little helpers that rely on code analysis, but thats just me.
Resharper seems to leave the option to us, asking us if we want to allow it to open all these files in order to have undo or not (and thereby processing faster - and making more use of the CPU) - maybe an option to look into?
Anyway thanks for your time