"Also, anyone have side trip suggestions or insights into the difficulties/ease of cross-country travel to the various lakes that dot Humphrey's Basin itself?"
Upper and Lower Desolation lakes, Mesa Lake, Tomahawk Lake, et al, are all easily reached cross country. There is a way trail that leaves the Paiute Creek Trail and takes you past Lower Desolation Lake and on to Upper desolation Lake. It is easy cross country from the south end of Upper Desolation Lake to Mesa Lake and on to Tomahawk Lake. From there you can drop down to the Paiute Creek Trail. On the south side of Paiute Creek Trail, nestled up under Glacier Divide, is a gorgeous lake appropriately named Honeymoon Lake. You have to cross Paiute Creek to get to a trail leading up to it, but it is well worth the effort. It would be a primo place to spend a night.