Field Closure opens a new can of worms, discussed somewhat under the 'parked' thread, whereby a coordinated- or even maverick- assualt might well close all of one side's bases. Not good.
I think downgrading a base would do what advocates of field closure desire regarding a capped field, but have little effect on non-capped fields.
By downgrading, I mean having a spawn delay- preferably one based on some damage done to the field. Damage could be either to the hangar or to some yet to be introduced target(s).
Example: Have 6,000 lbs of bombs destroy a hangar (maximum damage, then it begins to rebuild). Up to and including maximum damage- each 1000 lbs of bombing causes a 5 second delay at the spawn point before an aircraft's engine will start. Thus with the hangar destroyed, each aircraft which flies from the
field in question would sit for thirty seconds before takeoff.
A thirty second delay at a capped field comes pretty near closing it. Thirty seconds well away from the action doesn't change much.
Naturally the numbers (damage/targets/delay) in the example above could/should be adjusted based upon analysis and/or experience.
I think this proposal is of similar implementation
complexity (for the developers) as a field closure scheme, accomplishes the objectives of the field closure concept, but is a far less dangerous idea in terms of undesirable collateral issues (i.e. the aforementioned can o' worms).
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Pavel