I think with Campbell, we're just seeing an extra/bonus option, that we can bring in to freshen things up a bit with no effort or expense. I know I said that I think we could do with bringing in a couple of forwards this window, but why not make it 3 with Campbell, and completely freshen up the attack?
As you say, none of our current forwards have totally convinced: I'm not as anti-Giroud as some, and still think he's a useful option to have in the squad, but he's clearly not a striker for all occasions, and doesn't have the stamina to play every game; there's something clearly not right with Podolski - don't ask me what, but the manager obviously isn't sure about something there; Bendtner is definitely going, so no point in even thinking about him; Sanogo is long-term gamble who may never come good; and Walcott is used more on the right, is injured quite a lot, and probably isn't built for playing as a lone striker through the middle. There's also not a whole lot of variety there either? Walcott's probably the only one who offers us anything drastically different from the other 4, and even he doesn't have a lot of power to go with the pace.
Purely from a playing POV, I could happily lose two of those players this summer (e.g. Bendtner and one of Podolski / Giroud), and replace them with a world-class striker and an additional wide attacker / occasional CF (like a Remy), or a goal-scoring winger / wide attacker (Griezmann / Draxler?), and I really couldn't give much of a shit about putting even more players in Sanogo's way, so I'd be more than happy to bring someone like Campbell in to compete with him and hedge our bets with the young/potential players.
And that wouldn't even take too much more work eitherr? Campbell would take no work and would cost us no money, someone like Remy is supposed to be available for knock-down fee of something like £7m, and would probably jump at the chance of joining us, so that pretty much leaves the big name CF as the only tough deal? We need that main CF anyway, even if we only go for one striker, so it's not really that much more effort...