Track comments without any track mods for now.
1. The train approaching the roundhouse with a train on the level track: Drop train, turn engine at house, go upgrade to far distant crossover to pick up train again, this time coupled to caboose? A little cumbersome and unusual I think.
2. The train approaching the roundhouse with a train on the DOWNGRADE track: Drop train (CAN'T ON A GRADE).
So think about having a double ended siding on the level track, arrive, drop train, run around, grab caboose, run around, turn engine and caboose, spot caboose on end of train, run around train, pick up train, head on out. Works for me!
My 2 cents worth spend it wisely! Russ