BBRSP is almost to big to squeeze into a weekend but can be done. I drove out the day before, slept in my car and pushed off the next morning. Rode for three days and drove back on the fourth. This was a bikepacking trip on the Epic Loop so logistics might not apply to the type of campsite trip you're asking about.
If you camp near Lajitas, you can ride from Barton Warnock into the Contrabando, Fresno Canyon, Dome Loop trails. Perhaps split up as morning and late afternoon rides. Or ride the Epic in one full day. All of these areas have interesting historic sites to explore and break up the riding. Airport trail is close by as well. If you leave early, you can ride that same evening and vice versa on your last day. So two days of driving/riding and one full day of riding. Totally worth it. Beautiful scenery, amazing sky watching, and solitude.
Where is Iron Mountain? Never heard of it and not getting results on a Google search. Thanks!