I don't want to come across as a sound editing expert because I'm not, I just dabble a bit and have read a few articles.... but my guess is that the Trumpet Soloist was recorded closely in the higher register and the vibrato isn't as suitable when playing lower notes.
What you're intending to do sounds like the right way to go to me.
I did a recording a while back where I had set a few different trumpets, with touch-enabled effects, into different panel memories but then found that they were panned to different locations etc, so basing several different Trumpet sounds on one original setup is definitely the way to go. The result of my recording, even when I had adjusted the panning, sounded like different trumpet players playing alternate parts of the song so that went down the pan. Especially when I discovered that the sequencer hadn't recorded the aftertouch!