I think you are trying to do too many things at once, outsourced to FAA land, while your NAA is in the process of extracting itself from EASA land, under much uncertainty.
The short answer is no, not feasible. Long answer: you could do it with a lot of IF's and more planning and preparation then what you currently anticipate. Are you currently in a SOLI process for your ATPL? Are you keeping the UK as your NAA? Do you hold an FAA pilot certificate issued on the basis of a foreign license? Do you hold a stand alone FAA certificate? A lot has changed since you last held a SEP-SPA license and there's a lot going on right now. The best option for you also depends on your future plans.