Whilst a lot theoretical sense is being spoken here I think one needs to look at how, where and if such "mid-range" airlift would be used. If we consider current ops we have two (Helmand area) main airfields and then a bunch of FOBs, none of which are served by tarmac/TLZ. Your C17 brings the outsize vehicles into the big airfields which are then driven to where they are required. In an ideal world these would "spoked" out to TLZs by the A400 and everyone would be happy.
Unfortunately, this is where theory and reality bid each other adieu. An aircraft is at it's most vulnerable when landing/taking off or offloading on the ground. Risk aversion, fear of litigation & all round arse covering amongst the Air Staffs has reached such heights that the use of TLZs is seen as being so risky it's not worth bothering with. If these vehicles can be driven to where they are needed then that will be pushed for. Unless we build another new, large Bastion style fenced-in, secure TLZ the A400 (or C17) will not be delivering anything to patches of dirt anywhere.
So where will our new, shiny A400 be taking all these heavy vehicles? I guarantee you that they will fall into the strat-trap that the C17 finds itself in. They will not be infilling vehicles into TLZs as their airships will be too fearful of losing one and they won't be doing airdrop because a) the C130 can deliver enough of that and b) they're much more useful stratting stuff into theatre.
The A400 may well be a very capable platform but the reason I would hesitate to go fly it is the same as I would never fly the C17: the only interesting flying either do, or will do, is NVG MOS circuits at Keevil. No slur intended on either platform, just an observation of reality.