Is there no shame?
To be totally honest, if all the weapons were stuffed into the arms, I wouldn't care one bit. Longbow arms are like Archer torso bays; they're huge and stuffing a wide variety of weapons into them is common. I seem to recall a 3/5 movement, dual AC/20 Archer that appeared in a Cincy game once long ago (that may predate you and Phil, though). Anyway, the biggest issue with that Longbow is that it doesn't have the side torso armor to deal with the amount of firepower it's going to attract, with an XLFE underneath, and without enough movement available to be able to keep its TMMs high enough so that most of the fire misses.
I probably would have set it to 3/5/3, kept an SFE in there, and thrown a ton of lasers into the arms, were I running it. Longbow OWs are a hard thing to work with and still keep them credible in an environment where recovered tech starts popping up. Maybe something like this, which has better long-range fire past 15 hexes, equivalent medium-range fire between 6-15 hexes, only gives up a little short-range firepower, will have the same TMMs, because of bracketing fire will have roughly the same heat efficiency, and doesn't have an XL engine (the MPLs could go in the arms too, I guess; they're in torsos for crit-padding). Admittedly, it *is* slower by 1 MP, which can cause reinforcement time difficulties, depending on how the average speed for the lance averages out.
Now, what I
am looking forward to Xotl's maintenance rules revision dropping, though. Adding additional CBill costs "per weapon" (ballistics cost least, missiles cost middle, laser/PPCs cost the most) is both a fantastic idea, consistent with the fluff, and gives a reason why everything in-universe isn't "laser spam forever".