Even if you keep the same hardpoints, I'm willing to bet it will still be a metric crap ton of c-bills to customize the mech.
That aside, here's the formula for a PPC catapult with the C1 variant that is the founders mech....
Removing the 2 LRM's and ammo nets 16 tons, plus 4 more for taking off the medium lasers is 20 tons. The most basic configuration involves mounting 1 PPC in the Right Torso, 1 PPC in the Left Torso (total of 14 tons thus far) and putting an SRM 4 (with 1 ton ammo) in each arm. This results in a machine with 15 heat sinks and 10 tons of armor, so it's rather lackluster.
The next level up the customization scale involves Endo Steel and Double Heat Sinks. If you have access to these and can afford them, Endo Steel nets you 3 more tons to spend, and you can crib 1 additional ton by paring down to 14 double heat sinks. This allows you to upgrade to SRM 6 racks in the arms and bump the armor up to 12 tons.
For those that like, can find, and can afford XL engine technology, you could swap out it's regular engine for an XL engine of the same size, which would free up another 6.5 tons. You could add 2 medium lasers in the center torso, an ECM pod, another double heat sink, and perhaps upgrade the SRM pods to Artemis Fire Control (if it's implemented in game, not sure that it is). Or alternately, you could bump the engine up to a 325 XL (and a slightly larger gyro) and gain a mere half ton, but increase the mech's ground speed to 88kph.
Lots you can do with a mere prime configuration, and my ramblings are just suggestions. Nearly anything goes if it fits in the hardpoints.
Edited by ScrapIron Prime, 28 June 2012 - 05:52 AM.