There is a short item in Modern Railways about Bow Street. It mentions students walking to the campus. I can't see many wanting to walk a mile along an unlit A road.
Looking at the train times it would just be possible for a bus to connect out of the down train and into the up train. It wouldn't work if the down train was late though.
Realistically its largely used for postgraduate and office space (I believe they've also built a new innovation hub there as well), undergrads, for the most part, don't have to use it as they tend to use the main campus in town. It's likely that due to the infrequency of the buses up to this point that if you work there then you probably drive.
Unless they've created a new bus route, the existing buses don't actually travel between Bow Street and the University Goggerdan campus, there is a 526 bus that goes to the campus but that actually leaves from Aberystwyth station (not going via Bow Street) so if they want to connect properly then they'll have to fiddle around with the routes.
Having driven along that route, I don't think that apart from on a reasonable day the path is a fantastic option, as you say it's unlit but there's also nothing much in the way of shelter so if you were doing it regularly for non-leisure usage you're gonna get very wet at some point.
In my humble opinion, the station at Bow Street is great for those who live in Aber or Bow Street and who want to travel between the two (or further afield from Bow Street), its also good for the outlying villages but only if you have a car to get to the station or you're on the main bus route.