This is something I threw together a wee while ago whilst trying to make KE rockets a viable shoulder option.
Head Yugiri mdl.1 (light CE head with great internal performance in every category)
Core CB-402 (lightest CE core in the game)
Arms AC-129 Vlad III mod (highest firing stability arms modified to reduce weight/drain)
Legs Le2L-B-V15 (light biped legs with best load and turning)
Booster BA-309 (acceleration type with lowest normal boost stat)
FCS Fs-L-M24 (lowest drain wide-angle FCS)
Generator MAKIBASHIRA mdl.3 (highest capacity generator)
Arm units Au-F-K16 (highest damage HEAT howitzers tuned fully for power)
Bay units HATSUKARI mdl.2 (highest damage pulse machineguns tuned fully for power)
Shoulder unit SL/RCB-203 (highest explosion damage KE rocket)
AP 22530 KE 1180 CE 653 TE 423
B 115 HB 363 RR 1044 T 1062 EN rec 4188
The frame dumps defence completely and is not as fast as other lightweight bipeds. It is however supremely mobile and has enough load to spare to mount a fairly impressive weapon set. HEAT howitzers are the primary weapon on this build, with the other weapon systems providing coverage and a way to quickly destroy enemy shields.
Given that piloting this AC effectively requires you to manually aim two weapons with different trajectories at the same time whilst also dodging every one of your opponent's attacks, it's fair to say that it is a challenge to use