In the current climate, the idea of governments putting in a lot of cash for a game or two of rugby union at Super level is a bit hopeful. Maybe they would put in a top-up amount to supplement other sponsors bringing an event to their location.
Decent crowds for any relocated matches would be important but, on their own, probably wouldn't be enough to justify the change. Reckon it's more realistic to look at getting commercial sponsors, with the reason for moving some home games being to give those sponsors a bigger catchment (all the other Australian teams have base populations of 2m+).
The Western Force's method of getting separate sponsors for their 15 starting jerseys also shouldn't be dismissed by the Brumbies - even if they can't get all of those in Canberra.