I'd swap Johnson for Johnson, and throw money at Richards to replace Carra. This in addition to Cahill, not either or, because Agger/Krygiakos/Sktrel aren't good enough often enough (Agger is certainly good, but if he can't play half a season then he needs to be shown the door).
1. City won't be selling Johnson.
2. You having a laugh about buying Richards to replace carragher, who is still by far the best defender we've got at the club, his experience, leadership skills and organisation skills are second to none, and to pass that experience on to younger defenders at the club is invaluable. Richards is a shocking defender, and is to reliant on his pace at times.
3. I agree with getting a cente half, Cahill for agger, and maybe one more
4. Glen Johnson is still one of the best attacking full bcos in the country, and its only making things more difficult by getting rid, when we could do with keeping the quality thy we have got in the squad