4350 rail ejectors. I've played around a lot with the placement of the ejectors and came up with this configuration of ejectors for the highest number. Nominally this uses 174k/m solar sails, but I haven't gotten it higher than 140k/m, it has 4 less artificial suns than needed for 100% uptime.
Import: proliferated strange rods and proliferated solar sails Shoots: ~140k/m solar sails maximally, depending on planet and swarm orbits Power: 16 GW
Blueprint black magic: - Used the blueprint slide technique to insert power poles 'too close' to ejector. Also the suns make use of this to get more of them in the space of the ejectors. - Used lengthened belts everywhere to greatly reduce belt count - Used telesorters to reduce belts