I chose the "all of the 3" option.
Why?
Well, once in a while, having a "fun" strictly-stock no rules server is a fun way to vent steam. Let the players get their BB-itis and fleet-ism out of their system, bag a homeworld or 3, basically do what used to happen on the I-play servers.
However, that didn't work on a solid consistent basis before, and it won't work now. We need servers with rules and additions (mods). There might need to be a lot of rules to cover the problems / inconsistencies of the game / will of the Admin, but as long as they are worded simpily and clearly even long rule lists aren't that much of a problem, especially if a core set of rules becomes common.
As to downloads, no download is "optional" if it is mandated to get on the modded servers. Especially with our penchant for chaining our servers in a string to keep the player-base on each individual server up (I don't think any but the "main" server on the lists ever has more than 20-30 registered players). There should be a simple "core" download, relatively small, and be used for 80-90% of the modded servers. OP+ with no models could fit the bill, if it is chosen to be the main download. The shiplist / fighterlist as a separate download is small, and if configured to work with the "core" mod, people on 56k can handily afford to spend 1 "average" mission's worth of time (5-10 min) getting the touch-up for that particular server. Occasionally, having an expansive mod that takes a while to download isn't bad, and adds spice & vareity to the game. I'd just recommend locking down the mod early, making it available to the masses well before the start of the server so it can be downloaded (peacemeal if necessary) prior to the server's start.
There's room for all 3, it's just a matter of stabilizing the fan-productions to a point where they don't need to be consistently updated. This last point, in and of itself, will probably shave 90% off all future "mandatory" downloads...