You'll be able to switch back and forth with the HHKB if you give it enough time...
Rather than hack my way to something consistent, I just tried going back and forth between it and another keyboard and at first it was a real pain...enough to where even though I really liked my HHKB, I considered selling it because it was becoming really inconvenient...
At some point it just clicked and now it is completely normal to switch back and forth.....I'm not sure how or why that happens but it does...It is like getting used to driving on both the right and left hand sides of the road...You eventually get used to switching back and forth (if you're in a situation where you do).