--- and one more opinion --- since you already have a Futaba radio that came with the Nexstar, it makes sense to continue with Futaba for reasons of receiver compatibility, plus you can link your two Tx's together with a buddy cord if the time comes that you will be teaching other pilots.

Futaba makes good radios with all of the features & goodies --- just like their competitors. Why not stay with them?

The 4* is a good second plane

Warbirds are nice second planes until you try to fly them without adequate experience -- then they make great spare parts.