Really though, I think simply turning of factorization silver would be fine. The other 2 mods provide enough silver even for factorization, especially if you pulverize your lead.
I was thinking the same too. From my Tekkit days, I had loads of silver, and nothing to do with it. The amount needed for RedPower was minimal.
If you are using Factorization builds, chances are you are not going to us other machine systems, so won't need the silver for those.
If silver is a shortage for your server, well, that's where MystAges and Twilight Forest come in as other sources of ores.
Haven't checked, but I assume you can turn off Factorization Silver Ore generation, and use other mods silver in Factorization recipes? If so, I'd be included to have the mod enabled, and might even use it (there's soo many new things to learn!)