Limiting it to no more than 2 Chars by the same person gives the server a lot more possibilities for Interaction, On our Old Server PTC/Chaos that's all we where allowed is a Max of 2, and we never had any problems. the restriction was CAP Ships, Military and Pirates only one per Person. So a Military group could run a Repair ships transport etc but not another Military ship etc same for the Pirates they could also run Repair ships and Transport class ships as well.
It worked very well.
Our Server also allowed Multi Boxing so we could log 2 ships on the same PC and just Alt Tab between them.
The reason is the people without 2 Computers didn't like others doing it that had 2 Comps. and they could not.
and for POB's made it easier to keep up with bases. didn't have to spend all day trying to keep up.
But it was allowed to Mine and fill your own transports or others with your transports there. it sure didn't hurt the game or the Interaction. if A Pirate caught them they always paid double