Wow quite a lot of responses and lively discussion here, thanks for the input!
I can now at least see the train of logic in putting best condition tires on the rear. But here's my follow-up: If you believe that worst condition tires should go on the front always, then surely you must never rotate your tires ever, no? Assuming (for FWD at least) that front tires wear more quickly than rear tires, and that you are starting with fresh 4 tires, the front tires will ALWAYS be more worn than the rears, and therefore you should never rotate them and reverse that condition. Furthermore, the difference between wear/performance will only exaggerate over time making it even more important to never rotate until you need to replace the fronts. Otherwise, this logic totally falls apart unless you only replace your tires in pairs and never ever rotate them. However, clearly tire manufacturers recommend (and even require, for warranty) regular tire rotation, so there is some kind of break down in the logic.
To me, the purpose of rotating the tires is to even the wear across all 4 tires, and get maximum life out of all 4 before replacing all 4 in a set. By rotating at a certain frequency (usually 5k-10k miles?) you are always in a condition where the fronts and rears are basically at the same wear/performance level, and these concerns of bald tires in the rear and good tires in the front causing handling concerns never really enters into the equation.
With this in mind, I am going to go ahead and rotate the new tires to be up front. I looked at my records, and the "old" pair of tires are around 3 yrs old and just under 20k miles. Not that much for a tire with something like 640 wear index and 80,000 mile warranty (Michelin Primacy MXV4). I looked at the tread and there is no problem at all. They are not close to bald, in fact arguably they have just as much tread as the new tires. (The Michelin Primacy MX4 have a little deeper tread new than the Premier A/S which is what I got as replacements since the Primacy are discontinued).
In this case I do not believe there is a major difference in tire performance since the old set are still relatively new. I will put the new tires up front to get them to wear faster and just rotate as normal moving forward, maybe going a little extra before I rotate again. Down the road when the old pair is ready to be replaced, I will just get all 4 new tires and sync everything up again.
Probably I will drive around with the tires as-is for a couple of weeks, and then rotate and see if I notice any difference.
