A pair of LRM15s is a ton lighter than a trio of 10-packs. If your goal is a constant rain of missiles you are best off with a Mad Dog, Catapult A1, Archer (any of them), Orion VA or something similar and pile in at least 4 or 5 LRM5 packs. In chain-fire mode, those mechs can create a fairly steady rhythmic thumping of LRMs on a target that is sure to annoy. (Note that this tactic is easily defeated by AMS.)
If your goal is just to toss out a decent cluster of LRMs at a time, you are best off with 15 packs. The LRM10 and LRM20 are the least tonnage efficient launchers in the LRM family, the most efficient is the LRM5, the 15 is a good compromise between tonnage and hardpoint efficiency.
As for the Wolverine, if you want to do LRMs on it you are best off with the model 7K. A build like this should work:
https://mwo.smurfy-n...23c89a9012f8a8e
To be honest, however, there are several options for mobile LRM platforms at the high end of the medium weight scale that are probably better.
As for XL engines, as a general rule you use an XL engine to attain better speed. If you use an XL for the sake of more guns you become a glass cannon. Don't get me wrong, glass cannon builds can work, but if you aren't 100% on top of your positioning you will only get out one or two alpha's worth of damage before you get eaten. At 55 tons, the 300XL will serve you fairly well, it's a good compromise between tonnage and speed. Also, most of the 55 ton mechs have large arms, so a little torso twisting in combat will let you use them to shield your side torsos.
XL engines in Inner Sphere mechs are basically a "must have" in lights, strongly encouraged in mediums, risky in heavies, and questionable in assaults. And I say that as someone that is crazy/foolish enough to run most of his Zeus and Battlemaster mechs with 350+ sized XL engines.