All-grain 20%+ beer

I've been reading all the threads about brewing 120min clones and have gotten a lot of great advice. But, I really want to do something that's no more than 20% sugar (ideally 10-15%) and the rest malt. I've read Johnny Max's article on BYO, but I have a few more questions.
I plan on doing something akin to his method, mash overnight with about 25-30# of grain (I have a monster 70qt cooler), boil 8gal down to about 4.5, and use 099 as my primary strain. Couple concerns:
I've heard 099 is pretty terrible for ester production, can temp control help much? Pitching any yeast into something around 1.200 regardless of how much volume seems to be asking for trouble (If I bring down the all-malt wort to 1.150 and make up the rest with sugar additions, would I be better off?).
Other than that, any advice on brewing these types of beers?

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Just blue-skying here but what about pitching a more mainstream strain into some 1.080 and then making additions of 1.2 as the fermentation proceeds?

This is by far the most comprehensive 20% ABV thread I've seen to date:

https://www.homebrewtalk.com/f12/way-way-way-over-top-sam-adams-utopia-clone-91463/

Lot's of good information in there regarding yeast strategies, etc...