the whole venerable battle barge idea. Put simply, all warships after the horus heresy, venerable or not, were removed from the hands of the space marines. The whole "find or capture" idea doesn't pan out, because the Navy would claim it and take it. While the Marines can argue with the Imperial Guard, the imperial navy has final say on any recovered ship, and are probably willing to maintain the check and balance on the marines with lethal intent.
I can see a vanilla barge customized and kitted out post aquisition, hence the chapter specific barges. Venerable barges selected from the other battleships? Hell freakin' no. Giving space marines access to lances, nova cannons, and huge launch capacity is just taking it a step too far for the rules, and for the fluff.