I've done a couple of Berliner Weisse batches with no boil. Fairly easy for that style as it doesn't need much, if any, hops. Last few attempts have been mash with some Saaz. When the mash is done bring it up to 75C/167F. Cool, pitch the wheat yeast, let that finish out, then add the lacto and brett, give it some heat and package a week or so later. Tastes like a wheat beer for about 2-3 months then the brett kicks in and the wheat beer flavours fade and it turns into a lightly tart, fruity, slightly funky ale that's very refreshing.
The isomerisation happens at mash temps, but it's ridiculously inefficient and I doubt anyone has done the research to work what amount of iso alpha acids are created. I think your idea of boiling separately makes sense.
it's actually an old practice from northern Europe. When metals were considerably more expensive people would mash in wooden containers then add hot rocks to get to wort up to pasteurisation temps. While it was mashing you'd boil the hops in some wort in a copper pot separately. I've heard a German brewer talk about that as the real reason decoction mashes were invented. For isomerisation, not concentration of the wort.
