I don't like the idea of using the Wrangler and frontier justice together because then your personal firepower amounts to melee, 3 shotgun shots (likely without very many crits because you want your sentry to be alive.) and a sentry that aims imperfectly. So, the two loadouts I think will be my favorite and second-most favorite respectively are:
This allows you to have 150 hp and quickly make dispensable sentries (lots of revenge crits) and support your sentry with your pistol. Your sentry will die often but that's ok because you want to move it to be sneaky and you want revenge crits. This is the awesome battle/ninja engie layout.
The Southern Hospitality
The Wrangler lets you have a sentry-sniper and with a dispenser you have a dangerous little base. However, the sentry's aim is imperfect. I use the regular shotgun to provide plenty of personal firepower (6 shots) which I feel is necessary with not having a pistol. In addition, you can't really take advantage of revenge crits with a sentry that has a shield around it. The southern hospitality gives spies something to think about, although if there were tons of pyros I'd use the wrench I think.
So, those are the two loadouts I think I'll be using, especially the first one. Thoughts?