Unless I've misread your messages, the existing regulations under §§1.163-10T and §§1.163-8T already cover the ordering rules you are looking for.  Since TCJA does not rewrite §163(h)(3) but temporarily reduces the dollar limits for acquisition indebtedness and suspends deductions for interest paid on home equity loans, the existing regulations will continue to apply.

The only point that the IRS felt the need to clarify is that interest paid on home equity loan taken out to buy, build, or substantially improve the existing home, with which the loan is secured, will remain deductible under TCJA, to the extent it is within the dollar limit and the other conditions are met (see IR 2018-32).  Again, this is not a new law or regulation, only a clarification of how the existing rules will apply within the context of TCJA.