As I said no harm in trying.
Costing is a big issue and the return we would get from it, as these are not altrincham fans but another clubs fans who may not care for the club (Sorry UK Phil but you know what I mean) so can't guarantee people will use the facilities. Having people milling around near the main road having beer may not exactly please the locals, lets be honest putting a sign up annoys them !
I am just not sure of a large amount of away fans drinking alcohol in such an open place. too be honest it scares me. These are not altrincham fc fans but they will be representing the club, if that make sense. Their actions will reflect on the club, our club.
Get your ideas down and approach the club, no harm in asking as you rightly say but I need some persuading