I think a big issue as to whether those using their home resort most of the time will be better off or not is home resort priority. Whether, as suggested, week owners and legacy week owners converted to the new system both enjoy a home resort advantage and get to book before points owners, or whether legacy week owners in the new system get to compete at the same time with owners of every other resort, even when booking their home resort, will make a big difference. If the former, then even those who usually use their own resort might be better off as time goes on, but the choice will be different, at least for me, if the latter.
Of course, cost - both up front and on-going, as well as the impact (if any) on MF's have to go into the equation. IF Doug's guess is right on the fees, then a big factor for resale purchasers at least is whether that $1499 figure is for each or for all. I can see a $900 "penalty" or surcharge and would agree that it isn't too onerous if it evened out the playing field (unless we see other resale versus direct differences), but not if it is per unit, where the other charges are only $100 more for 2 or more units versus a single unit.
There are several other questions I need to see the answers to, including what happens with partial use and, of course, how are the properties being valuated?
I wonder if legacy week owners who opt to convert can still reserve a specific week to put into II, since supposedly they can choose weeks or points in a given year? Will that be restricted to personal use, use and/or rental, or use and/or rental and/or trade if so desired? If the point requirements for trading in II are akin to those of the Asia Pacific program, then exchanging in II for a high demand week required the point equivalent of premium Plat. Plus weeks, and even a converted owner exchanging for a non-Marirott in II might be better off with a strong week deposit- although that might not be an option.
The more I think about it, the more questions seem to crop up. I hope Sue is adding to "the list."