Bartok,
What you are discribing is why LODs were used. LOD 2 was the one most often used with medium resolution textures and a lowered poly model. LOD 3 was the far away one and had low resolution textures and a very low poly model. LOD 1 was only used up close had high resolution textures and a high poly model. now what normally happens is your ship flicks between LOD 1 & 2 depeding on the distance you set the model from you in the view. Enemy ships start off at LOD 3 and move to LOD 2, upon occasion if you get really close and have your ship close in the view it qwill make LOD 1 as well. The reason the LODs where there was to reduce the impact on the systems playing the game. It was also the reason so many ships never make it into mods, they don't have LODs and too many impact the system. Over time allot of ships got high res textures over all the LODs and it does make a difference, but not as much as not having LODs at all. Now adays most of us have systems were the effects are not noticed nearly as much, and most high poly high res ships don't bother us. You can still a difference but it is only in the mission loading time as all the ships are loaded into memory. It is odd that you can see it flicker the first time LODs are loaded, that you don't see with none LOD ships, though the load time is less with the LOD ships. Once the ship is completeky in memeory it is pretty hard to see any differeces in game play.
So currently it really seems only load time is effected, as no mission I can thing of loads the maxium number ships playable. I tried it out with 36 different ships all with LODs, all with no LODs, All with low res textures, all with high res textures. Mostly it was all in the loading time for the mission that varied once the game got going it was not so noticeable, all the spare time cycles for the processor get taken up by the AI more than the models themselves. The Process was tested against a AI and a friend on a networked PC, the networked players used less processor time over the AI.
So in conclusion LODs still make a difference but no one is really using them anymore, kitbashers usually don't. It seems that there might be a maximum texture size allowed as well but none of my test ships had more than 12 textures and 3 or less at 1024 x 1024. Load time seemed to be the most effected area, about 5-8 seconds variation could not be discovered, depending on the models used and the texture sizes. Note on the variation it would change using the same models at times, no reason why.
So models with LODs and proper textures to go with them increase the folder size, but work better than none LOD ships, but with todays systems it really doesn't matter much.