If anything class D is just the right mix of protection for IFR against allowing VFR to operate-its a known traffic environment-so traffic info can be given, and if you need to build in some 'leeway' you have the ability to do so ie not above a level etc
our zone is very active with not just the IFR paying customers but two flying schools, considerable circuit traffic (of all types) and all the transits you could want-many of these would not get the training/routeing they want if we had to provide full seperation-even using reduced in the vicinity-and we have few problems with the way we operate-just make sure every body knows what is going on and use some common sense-it certainly is not unsafe