Wanting a short-cage derailleur on the bike just because that's what you want is all good. They do look better and shift better, no doubt. And, yes, what you're planning will work, you're just pushing harder on the limits than many would do. It's just that there's tradeoffs. (Your're an engineer... you grok that there are always tradeoffs.) Here, the tradeoff you're making is that you get what you want, at the cost of a bigger failure band, with the possibility of a catastrophic faliure mode if you screw up badly enough. The odds of that happening are probably pretty slim... but sometimes Slim shows up and wrecks the party. (Slim is Murphy's crazy cousin.)
It'll work, for sure. You just have to respect the limitations that you're building into it, which it seems that you do.
--Shannon