1 – Have you verified that there is no soft prepayment penalty for the loan that you get from the in house lender?
2 – Have you thought about what may happen if the home does not appraise?
Bugs or other appraisers may give you comments on appraisals of new homes.
Your plan may or may not work out but I am leery about it. To be honest I am concerned it may not work out but I could be quite wrong. I would also talk to some other lenders to check to see if your idea will work, if they will provide the financing on a new home immediately after your purchase.
As far as the home inspector, do you feel that there are problems with the home? If the home inspector finds something are you sure that the builder will remedy the problem? The short answer is yes, of course an inspector has the ability to find many items that you do not know about. The question is will the builder remedy them. It depends on the purchase agreement.