I no longer use routes without ToD4. DTG may consider making rolling stock on old ToD3 routes available separately. To make everything worse there are the loco dlc's (for example BR 182, G6, BR 101 etc.) connected to a specific route. I find all the TSW trains very beautiful (including the very first DB BR 1442), but this is not the case for the (now dated) routes. My HD is crowded with bytes I don't use.
Just know that it's not a perfect rendition since it's made by modders, not dtg who have the official tools. You'll see some weird lighting stuff happening but as long as you play at the right hours, you'll be fine
Whilst for pc, this mod may be a solution I think the original suggestion point still stands. On Xbox you still have the same problems with old rolling stock. And with new rolling stock, if you put them onto an older route, they appear obnoxiously bright.
An idea would be to add in the "filters" of the menu the possibility of "hiding" the routes that you are not interested in, and at the same time having the possibility of using the rolling stock contained in them.
Yeah I have quite a few routes (mostly German) I have installed purely for their rolling stock but never play. Would be nice to have the space freed up.