Second, although the water is well heated when the engine is working
hard (11 gals heated to 150+ easily in under an hour - if its already
warm it only takes 20 minutes to get hot) when the engine is used for
battery charging it never gets quite hot enough, and thus never quite
does the job

Heh, not a problem here. Twin 6.0L V8's get that water PLENTY hot in no
time flat.