Why would you want to go over the bridge? If you did you'll find that BRS only offers departures to FUE on a WED. Same for EMA/GLA/HUY/LTN
Of course you could fly from BHX on a sat with TCX or FCA. But you wouldnt arrive back in the uk until gone midnight, then have to face hotel costs or a 2hr+ drive back to wales in the early hours? By that time you'd be tucked up in bed ready for work on Thursday if you flew into CWL
Both of these flights are being offered by completely different tour operators, yes it would be nice to provide more choice, but as LSG has pointed out above, its a perfectly logical decision.
TCX will only be part basing the a/c. The a/c may be required to operate a route from another airport on the saturday, which is why its only at CWL SUN-WED.
I think it's only in the past year or so that TOM have had flights to FUE from CWL in the summer. I think Airtours/Mytravel did it for a few years tho, but stand corrected if I'm wrong
TOM havent operated to FUE in the summer for a while. They picked it up a few years back during the winter after MYT pulled out.