I agree with Kaneco, if there are specific things to change that would help the map (I'm thinking ammo on last point, reduced spawn timers by a few seconds etc. rather than big changes to the map like a new choke) then an email to valve would be better than making a _pro version that is unlikely to catch on.
And it is unlikely to catch on, given that viaduct is the only pro version ever to be accepted when there are countless others (a different granary_pro, badlands_pro, gravelpit_pro etc.) They just don't gain enough traction since there's too fine a balance between not changing too much and making it better - you always end up with debate.