01ACRViper

the Mesa de Anguilla and would give you the remote challenge you want. there are 2 approaches: one from Terlingua Abaja that requires some tricky rock climbing (not reccomended with a full pack) and from the NP trails that begin in Lajitas. Most trips up there are 2 day: one to hike to camp, the next day, hike to the rim and back down. there won't be any water up there, unless you go quickly and get water from the Tinajas after this most recent storm. you are guranteed to not see anyone, save maybe a few rafters on the river far below. this is on my list for next winter, should be fun.

another place to look into is Big Bend Ranch SP. the Rancherias loop is the Outer Mtn Loop of the Bofecillos mountains: long, remote, dry, and beautiful. it's a 3 day hike, but can be done in 2 semi long days or 1 hellish day. something I did over my spring break would work nicely for you. it was also in the ranch, though it isn't a marked trail. I walked up fresno creek to Madrid Falls, the second highest waterfall in Texas. it was roughly 8 miles one way, and flat until the very end. gorgeous hike, i plan on going back very soon. for a longer trek, conitnue north on the creek up into the Solitario, just be warned the last reliable springs are near MAdrid falls.

as for the Guadalupe Mtns, up the Tejas Trail to bush mtn, down blue ridge trail back to the tejas trail and down McKIttrick Canyon is my favorite hike in the park.