As someone that was formerly stationed it Texas here's a quick rundown. Leases are a contract as such it depends on how it's written some allow guests some don't. All game animals a subject to the applicable seasons which vary by county and zone. Many leases are multi year so for someone on TDY orders probably not a good option. When I was stationed in Texas it was at Ft Hood which has good hunting. The bureaucracy is a pain but as a service member it should be manageable. For non public hunting dove hunting after the first two weekends can be very affordable, then day hunts for hogs and javalina, day doe & spike hunts, exotic doe hunts, goats and non trophy sheep, all are affordable. You've talked to Mulie Mike send him a PM and see what kind of pricing. On your license deer tags are included but other game may require a tag google Texas hunting license and you can read the regulation pamphlet on line

Do people ever sell their lease for a year if they can't make it out to hunt? Or maybe if the lease allows 4 people to take 8 whitetail and one cant make it out can the substitute another person in?

Leases do become available and some have guest privliges. The Migratory Bird Forum has a lot of good links some with public land info http://www.texashuntingforum.com/forum/u...un#Post1888119.
There may be some opportunities throuh the Rod & Gun Club don't get so fixated on getting a lease you let other possibilities go by.