What method(s) should be used to shrink the map file size?

In order to make the server as blazingly fast as possible, I want to switch the map file to a RAMDISK, so the entire map itself is constantly loaded into RAM. This would mean that it's nearly instantly loading chunks. Currently, chunk loading is about half of the 'slowdown' for the server (the other half being the anti-cheat, throttled by the CPU).

So, I want to lower/limit the map file. There are ways to do so, and I want your input on which ones everyone would prefer.

Personally, I want #3, and I'll just keep it 'trimmed' of the unneeded ones, hopefully keeping the mapsize relatively low.
#4 would be the ultimate prevention, but it's not vanilla, it sucks having to do it, etc...
Both #1 and #2 have the possibility to 'hurt' peoples houses, but only in certain conditions. I won't go into details...

Delete chunks not used in x amount of days (2 weeks probably)

Delete chunks based on algorithm to determine non-player "stuff" (chunks where people just passed through)

Both 1 and 2

Limit the map length (map perimeter) to prevent the map from ever growing (probably 40k out)

vote