Section 163(h)(3)(B) defines acquisition indebtedness as follows:
("B) Acquisition Indebtedness.
(i) In general. The term "acquisition indebtedness" means any indebtedness
(I) is incurred in acquiring, constructing or substantially improving
any qualified residence of the taxpayer, and
(II) is secured by such residence."
The home equity loan secured by your residence does not qualify under the definition of acquisition indebtedness because the term is defined that the indebtedness must be secured by such residence.
Indeed you can borrow to buy build or improve and have that debt be acquisition indebtedness; but only when the borrowing is secured by that residence (or land). This is not true in your case as it was described.
The problem is that you borrowed against your current residence in order to build the future residence. So, the amount you borrowed on the current residence is not acquisition indebtedness for the future residence since the security for the note is the current residence.
There really is no recourse because of the wording of the statute. Yes, the law is what the law is and this law requires that acquisition indebtedness be secured by such residence.
I hope this helps to know what the law says even though you certainly would have liked to have a different answer.