I've tried an LRM apocalypse also... but pretty much ended up copying builds from my Stalkers.
I've run 3x20's, but strangely have had the most success with
This - 2 A15's, 2 x PPC's, tag, BAP
It's a hybrid, so you have to actually stare into the eyes of your enemies while you fill them with cheese. I play by self tagging at the back of a group - hit with the PPC's while i'm getting lock, launch, watch the target panic and try to get to cover from the LURMS, profit. Until you overheat. It's also slow.... not really optimised, and has ammo in the arms.
As a pure LURM boat, i've had some good matches with this:
2xA15's, 1xA20, 3 MLAS, TAG, BAP.
I always feel i'm wasting those awesome high torso energy mounts if I don't fill them with some sort of energy weapon, but you can remove them for an extra HS or some more ammo.