Hi again! I posted a while back about the Rocket, E2, Ruston 48ds, and the J70 tram. On the same topic of small locos, I think a LSWR S14 would be a nice addition to TS2021. It would be neat to use it for shunting/station piloting scenarios. Also a less-likely suggestion would be the LSWR Drummond F9 due to its peculiarity and charm, but it might be too much work for the little use(I would use it lots....) it would get. My last suggestion is the LSWR Beattie 2-4-0 well tank engine. Its just a beautiful specimen of steam power and would be perfect for some branch line runs. I seem to have a theme of LSWR engines today....
There's an E2 here. https://steamsoundssupreme.com/ And you might find something of interest here. https://caledoniaworks.com/home/ And a forthcoming J70 here. http://digitaltraction.co.uk/mainsite/products/dt-lner-j70-tram-loco-pack/