Yep, all the trade offs can make a head spin! I think you found a good machine for your tasks; that warranty is impressive.
As far as extra lawns [I doubt you'd have any insurance or licensing issues just for that, but thought I'd mention it too]: if you're talking about too much more than an acre total, I'm guessing you'd be better off with the IZT tranny (just my take from visual "gut", and considering the applications by the various mfgs when doing the research like you). More than a few acres; you're looking at machines with pumps and wheel motors.
Just to throw in info I think you already considered: in the same price range you might look at a CC ZForce44; this gets you the Kohler Command 20HP, IZT, and pivoting front axel [your ditch may leave that argued either way], but you get a stamped deck instead of fab [not a big issue if hard abuse is not a factor]....I think another thread mentioned these being backordered anyway......
Anyway, I think that mini would serve you very well....and maybe a couple other lawns to boot, but I'd still add up total area and se if it's close to spec. Even at that, I'd think worst case your "20 year machine" may start costing some repairs a little earlier.
BTW: I just realized your name says you don't like yardwork....thought perhaps you were a old CC [IH] fan! /forums/images/graemlins/grin.gif