What do you mean by "loading down" the pickups?
Pickups need a high resistance across their output to produce the full spectrum of frequencies. If you split the output you effectively reduce the resistance across the pickups, killing your high end (loading down). Buffers help prevent this, by presenting a high resistance (impedance) to the pickup but not being loaded down by the circuitry down the line.
The triple switch you suggested, ehque, won't work because there needs to be a fourth position (off/off).
Use the volumes to control the output, you can mute it with the volume, and not the switch. Or were you planning on adjusting it on the fly, WHILE you are playing the bass?
Lastly, a rotary switch http://www.stewmac.com/shop/Electro...nobs/Rotary_Switches.html?tab=Details#details can seriously cut down some of the onboard clutter.