From what I read in there you're telling me you aren't going to spend the 300 bucks extra for some tyvek house wrap and flashing? I'd reflash, retrim, do all that. That is key for weather proofing. Not necessarily how many layers you have.
It's easy and you could probably at least do the housewrap yourself. Go get a 3/8 inch hammer tacker, and 2-3rolls of housewrap and a buddy and you'd be done in probably a few hours, considering 28 squares is pretty small. I've probably done over 30 in a day by myself using 60 minute(which I think is better than house wrap in some cases, if applied correctly, and is pretty cost efficient.)
EDIT: Bob vila, on your job, at 700/sq what is included? When I bid siding its about 350-400 a sq for clear bandsawn shingles, all with stainless application, and tyveking.