I think it'd more cost effective to have Channel 5 co-commission new shows with Comedy Central. They've invested heavily into drama and I think once that is established on the channel, comedy would be the next step.
They've done this before - a decade ago C5 commissioned a number of sitcoms, like Suburban Shootout, Respectable (the last thing the distinguished comedy producer Harry Thompson wrote before he died, shown posthumously) and Angelo's by Sharon Horgan, and they were all co-commissioned with Paramount Comedy, as was, with C5 showing them first. But it didn't last very long and indeed when Angelo's was being broadcast C5 announced they weren't doing any more scripted comedy.
And a decade before that, most of their early comedy shows like The Comedy Store, Festival of Fun and We Know Where You Live (the sketch show now only remembered for its amazing cast of Fiona Allen, Sanjeev Bhaskar, Amanda Holden and Simon Pegg) were also co-commissioned with Paramount and shown on both.
There were no sitcoms in that first batch and I remember William Phillips in Broadcast reviewing their first year on air and saying "we have yet to shudder at Channel Five's first sitcom".
There's nothing stopping them having success with comedy, they just need the right show that stands out. I always mention Celebrity Juice as before that ITV2 had pretty much no comedy but that took off, was very distinctive (I'm not saying it's any good) and ITV2 were suddenly in the comedy business with a genre that it could own. That's the kind of thing C5 needs to do, the problem with their previous comedy output is that it's often been perfectly good but not at all distinctive so pretty much ignored, and they need find a style or genre that they can specialise in. Of course a few years ago C5 did the most blatant rip-off of Celebrity Juice.