Yeah, most of the steam era equipment is out there now. ;D
The most glaring hole in the steam roster is the lack of a 4-6-0, which handled the secondary passenger trains and some local freights on the line. But 2-8-2's, 4-6-2's, 2-8-0's and 0-8-0's are covered. You could probabaly kitbash the I-GN Berks with a Kato Mikado mech and LL Berk boiler.
Diesel wise, the F's, E's, GP-7' and SW-9's are covered. Only the BLW road switchers and BLW and ALCo switchers are missing.
Magor Cabeese, I-GN boxes from Atlas, IM makes gons and reefers used on the Texas lines, and I imagine cobbling together either the heavweught Sunshine Special or streamlined Eagle cars wouldn't be too hard.
You still sure you want to freelance?