It would always depend on your expertise, if you're confident enough to do the 12 GPU builds then why not, its proven not a plug and play scenarios to make on this build and a challenging one,  I'm not against it, however, what I always consider is that once in a while a rig may fail and so as all of your 12GPU also idled, compared to 6GPU with two builds, you still have one that running when the other one fails.