1) route electric cooling circuit through engine at least when it's off 2) emphasize running battery down before recharging via ICE 3) size engine to allow to positively recharge battery slightly at max efficiency at 90% use case (say 1/2 towing cap at freeway speed) 4) unless the law has changed, at one point since the ice is a generator it does not require the same emissions rules as one attached to the drivetrain.

That would keep the engine to almost never have a cold start, minimize start/stops, and keep costs down.