Sorry to disappoint you, but with 10k-20k miles / year youŽre unlikely to get any meaningful status, if any at all, with any *A airline. IŽd probably join UA MP and hope for the occasional upgrade as a 3P/2P member (afaik 3P status can only be gifted to you by another status member), but as youŽre flying out of SFO, your chances of a comp. upgrade (unlimited domestic upgrades on UA/CO) are quite slim.

Please check the stickies in the United MP forum for exact info, but afaik as a 3P/2P member you get *A Silver status incl. business class check-in with UA and 2nd bag free.

Also UAŽs mileage requirement for upgrades arenŽt too unreasonable.