Yep-That Thermador simmer thing works really well. You can slow cook on your range top if inclined. I suppose you're at the mercy of some circuit board in the machine, but it seems to work perfectly. I like that feature and the really hot star shaped burners.
If I could design from scratch, I'd also want a 24 x 24 flat top griddle.
One other thing-having a really powerful roof mount exhaust is great. All smoke and grease fumes leave the kitchen NOW. Unfortunately, you can't run the fan and have fire in the fire place at the same time. Don't ask how I know.
Regarding the refrigeration, in an ideal world they would be separate units. With an additional separate ice maker. I think I'm going with the Sub-Zero where at least the fridg and freezer have separate compressors kind of like a commercial unit. Not that happy about it though.
What size SZ are you looking at? The new IT36C is coming out next month. 36" Wx84"H. The BI42 and BI48 are not changing.