Think of it as a lottery ticket. The odds are OVERWHELMING that they will blow you off… however if you don’t try then you have 0 chance of getting the prize. So no I don’t believe anyone will accept but I would not discourage giving it a shot. I have lots of friends, clients, etc who are trying it and nobody has gotten a hit yet. I have a client who sent in a 425k offer on a 460-480k priced home in Clairemont and they came back at 440k so we are negotiating. Clearly this is not in the same percentage reductions as you are looking for but it is encouraging. Give it time. Obviously the communities you guys are considering are not clairemonts of the world but in a year or two they may see the declines you are looking for.
Lets hope rates are not skyrocketed or if the rates are high, that the price declines compensate for them.
Also in your calculation are you including the interest (less taxes) you are accruing on your dp money? That does not totally make up for the lost deduction but it does count for something.