Back in my days at Aurigny, the ACI-JER route was very successful, twice a day service, and carried about 60% of ACI-GCI pax numbers. Sorry can't remember the numbers.
There was then a change in management and AUR went regional from GCI. What followed was, in my opinion, a deliberate move to get pax to/from ACI to go via GCI and use their regional UK services. The JER route was cut to one a day, and at a time (late morning) that was of no use to anyone, pax numbers collapsed overnight, and then the route was quickly dropped.
Rockhopper/Blue Islands came along and thought they could do better. They did fairly well in the first year but their eyes were really on the ACI-GCI cream.
The States of Alderney then made a massive mistake by granting BCI the ACI-GCI licence in competition with AUR without linking it to a condition of maintaining the JER route. No guesses what happened next.
BCI then did a period of ACI-JER fares but routing via GCI, which was better than nothing. The transfer in GCI was only 15 minutes, so no big deal. A bit different to AUR's 5 hour wait now !!
So yes, there is a market for ACI-JER provided the timings are suitable for business people, connecting to UK services ex JER, and shoppers.