I'm going to throw just one fact in here regarding laser weapons:
Not all types of lasers are able to be "fuelled" by electrical energy alone.
While this holds true for a certain range of lasers, many of today's industrial cutting lasers, for example, require the laser gasses to be replaced continuously, because the reactive components producing the photons degrade over time.
It is very well possible that your average lasgun can be recharged by simple electrical energy, but that a larger Mulitlaser with higher damage output and fire rate uses a
completely different type of laser. This might result in completely different maintenance and recharging necessities. The Multilaser might require a change of its lasant gas after a while, something that might be able to be safely stored in a Chimera, but could not be man-portable because of dimensons, weight or danger of exploding.
http://en.wikipedia.org/wiki/Laser <-- I suggest this as a basic source on a metric feth-ton of reasons why lasguns, multilasers and lascannons might SOUND similar, but could be operated in very many, very differing ways, giving possible reasons why they are used the way they are.