Your in a tough spot, USCIS doesn't really have a visa for multi-entry part-time work status.
Assuming you are a US citizen, you could sponsor your spouse-to-be for a green card, and then for the next 3 years, "reside" in the US (spend at a minimum 6 out of 12 months a year in the US). After 3 years (plus 6-12 months USCIS processing time, best case) your spouse-to-be could apply for US citizenship.
After citizenship your spouse could go to the US for a short or as long as they want, it only depends on the immigration policies of where you are now. If they permit dual citizenship then that's the best option as it offers visa-free unlimited stay at both countries.
It's a pain for 3 years, but you never know you may end up picking one of the countries to settle down in by then.
-ML
K1 -> I-485 -> I-751 -> N-400
Now filing I-130/I-485 for parent...