Thanks for your input!!
Viajero, I didn't know you were SCL based.... I'm heading there sometime soon. CO award ticket set for January (just before the rule changes) but may shift the date.
I've talked to friends who have been to Iguazu- sounds like an easy trip out of EZE or GRU. I hadn't considered Easter Island-- but that would be from SCL and would be attached to a different trip. I will have easy means to get to SCL or EZE on a future trip.
For this one, I'm looking at AA metal in and out- a nice and easy weekend.

It's one of those Fly Free certs-- not a OneWorld award, so Easter Island would be out of pocked from SCL- and in that event, I could use other means to get to SCL first.
Good tip about Colonia--- sounds like if I want to visit Uruguay only for the sake of visiting Uruguay, the short us$30 to us$55RT Buquebus BA to Colonia will fit the bill instead of going all the way to MVD. I'll bank that for future reference- and strike MVD from my list of options for this trip.
So.... La Paz is kind of out..... Montevideo is out..... just leaves Asuncion and Santa Cruz. Nobody has said much of anything about Asuncion-- I wonder if silence tells me something.
Side bar: Anybody seen Dinero Quemado? Takes place in Buenos Aires and Montevideo in the 1960s. Pretty neat.