The WP/VT&S 0-6-0s being a different make and model, I wouldn't call them 'variants' of a UP class. Note the larger boiler, smaller drivers, taller domes, different cab profile, lower, longer tender, ALCo standard appliances, and several other details all indicative of a different design standard.
That said, the group does have access to the specs for the VT&S engines. But if they are done, they will be done properly, rather than being shoehorned onto an unrelated project.