it's just the business section they struggled with, a 3 or 4 weekly service may make it easier to fill a business cabin,
Not sure about that. I had a couple of trips to do earlier this year when the CO route was have its seasonal "off-days" (Tuesday, IIRC), and it was an amazing hassle.
I had to *call* CO and tell them that I was able to book outbound BRS-BRU-EWR (SN to BRU, connecting to CO61), because their website wouldn't handle it. I was also prepared to support BRS by getting an ERJ-145 to BRU at 6.15 in the morning followed by a sweaty 45 minute dash across the entire airport (lousy airport for connecting) to get onto the CO flight. Less committed people would have just driven to London and got CO29 at 11:00, which gets in about the same time. And if you're going to do that, chances are, you're going to fly back to London, because so few people understand, let alone book, open-jaw tickets.
So I'd be sceptical that a 3/4 weekly DL flight would benefit from a better business cabin yield - it might be the opposite. 3/4 weekly to me (1356?) sounds like a holidaymakers' flight.