Experience transferring NISA to IBKR?

As a permanent (European) resident in Japan last year I opened a NISA account with Rakuten Securities. Since I didn't put money into it for months and I had serious troubles with their login system I moved my NISA account to my SBI証券 (my bank is SMBC so I already had a normal account there), which took few months due to back and forward paperwork. Eventually I was able to finally transfer my NISA into SBI and I would like to start using it this year on top of my taxable conventional assets there.

HOWEVER, I often travel overseas for long term work (which is troublesome to operate SBI証券) and, to say it "lightly", I am very unsure about the future of the world and specially Japan. Therefore I have been thinking that may at some point move out from Japan it is highly likely I will be forced to sell out my SBI assets. To mitigate this risk I opened a IBKR conventional Japanese account just to realise they have also the possibility of doing NISA.

–> My question is, would it be worthy to transfer my still empty NISA* account to IBKR in preparation to a potential future moving out from Japan, benefiting from the NISA system while here? Would that process take long?

*Only NISA, my taxable investments will stay in SBI証券

by OCA_doctoryellow