In the end it wouldn't really matter what level condition they bowled on, nobody would get awards as with 3/4 of the league unregistered, it wouldn't be a snactioned league. But as for selecting a condition, it would come down to the league working it out themselves.
As a bowler, I'm all for running leagues with tougher patterns. We have a sports league going at the moment, and I know that even though most of the bowlers are 10-15 pins under "normal" average, they are enjoying the challenge of the conditions and improving each week. Plus it's great to see Tonx get beaten by a girl with a 130 average
As a tech, I hate the idea of having to re-oil for leagues with a different pattern, but that's cause I'm a lazy bum! With todays oiling machines and the fact most leagues would be on average 18 lanes, it would only take 30mins to do the lanes, so if leagues are prepared to delay the starting time, it's really no big deal.
The main stumbling point, as mentioned in a few posts above, is policing the conditions. Not every centre is in the position we are and has access to a lane monitor, however all a centre really needs is the equipment to be able to take a tape reading before league. Then maybe the TBA or local associations could recieve these tapes and analys them. The USBC requires it for sports leagues and this hasn't stoped centres from running those leagues. In fact, sports leagues have increased over 130% in the past 12 months. I don't know of a single person in the industry who wouldn't love to see that scale of growth here.
In the end however, it would come down to an honour system, trusting centres are putting down the conditions they say they are. It would be up to individual bowlers to elect to their league committee people they trust, and for those committees to ensure the centre is doing the right thing. If they aren't, then find a centre that is!