Aside from those who buy every single route or DLC, I don't see this as a good idea. Especially since we don't know what routes get released until they are ready to be shown, and what kind of quality they will be produced at. It wouldn't benefit a player who only plays a certain countries route, it wouldn't benefit someone who prefers one type of service of another.
Season Pass would have been irrelevant, given the new German and US routes along with extended SEHS ended up bundled in TSW3. I think it works where the company has a plan and clearly outline what’s coming, as with the Snowrunner SP’s, but with what seems to be the chaotic production schedule at DTG, I’ll take each release on merit and more than likely wait for a sale to get a discount.
I think it's about time dtg got more organised. Not only would season pass offer a discount to people that prefer buying dlc this way but would also give dtg a big cash injection at the beginning of every year. There is of course the discounts offered by dtg and steam etc... but there's never any guarantee you're not gonna have to wait a while to buy discounted dlc.