I was thinking of using PDQ, actually. It's available in its basic form online for free, and with a good group it's fantastic.

http://www.atomicsockmonkey.com/freebies.asp

You could essentially stat out a young Miles (around Vor Game) like this, and it'd be fully playable:

Space Mercenary (+2)
Vor Lord (+2)
Bullshit Artist (+4)
Teratogenic Defects (-2)

It's obviously not a simulation system, but for the combination of high drama and low farce a Vorkosigan campaign would be I think it'd work great.