For me, I'm actually not really worried about our backline. I have faith in LRT holding down the CHB spot and C.Bolton taking the other tall - he covered quite a few small/medium forwards in 2005 (e.g. he held Farmer goal-less) but I see him playing full-time on the big bodies (like he've done all year), especially in the current times when the monster power forwards are getting endangered - all the big bodies tends to be playing more as leading forwards rather than the wrestling plugger/alistair lynch era.
The only times that Bolton had ready struggled was against the super-quick leading forwards (e.g. Rusling) but otherwise he had a great year. With Leo, I'm much more incline in putting him as a loose man (when we play a loose man) or taking the third tall. Dempster, Richards will take the other talls with Luke Brennan as cover if he's promoted (he got a lot of stick for his poor performance against Rusling - but if Bolton can't keep him in check, there's probably very few people that could on his good day). I really don't mind 'under-sized' full backs as the full forwards these days tend to be smaller with the bigger bodies moved to more CHF/Hybrid spots (Cameron Cloke and Ashley Hansen are good examples).
What we do need, however, is a KPP-type on the front line that is a reliable mark. We are an amazingly bad over-head marking team - our best is probably Ryan O'Keefe and as great as he is, he shouldn't be the main marking target up front. Big Barry Hall, for all his size, is a better leading mark than a over-head/contested mark, especially with the new hands-in-the-back rule and his tendency to drop marks. With Magic coming to the end of his career, we really need to find reliable options in our front line. The new rules favours the faster/high jumping forwards (e.g. Westhoff) as oppose to power forwards and that's probably what we should draft/trade for.
But there's not really a lot of these types that we should go for in this year's market (e.g. mcgregor is definitely not someone we should go for), so I suggest we actually don't shop around this year and instead looking for such a type in the draft (or hoping the likes of Grundy and Jesse White to stand up) and see what the market will be like at the end of next year (We might be able to nick someone useful from Geelong due to a lot of players over-performing this year and with Salary-cap tightening).