[DS] Heavy Weapon Teams [SG] Laser weapons

I was re-reading some notes of my own last night prior
to recreating a simple system I had written to generate
infantry squads using Steve Gibson's alternate infantry rules
when the following thought occurred to me.

I had incorporated a house rule that classed size one weapons
into energy using and non-energy using (based on whether they
had any power plant limitations in the design rules) and said
that infantry could carry any non-energy using size one weapon
effectively DFFG/1 and RFAC/1 IIRC as well as APSW's, GMS/L and
Light Artillery. So the questions are:

How realistic is the idea of a small team (say 3 troopers)
humping around a 20mm Auto cannon and enough ammo to make it
worthwhile?

Is light artillery the way to model a mortar team? How many
markers should they carry?

One of my Star Grunt units is based on the Steiner laser infantry
platoon (from Battle troops) these guys are all supposed to be
armed with laser rifles and have lasers as their support weapons,
I could model these as say FP2 but high impact say D10 with the
support lasers as a HEL/1 but how about a HEL/0.5? what would it's
stats be?

[OT] The programme was eaten by a hard disk crash and did vehicle
design as well my language was "colourful" to say the least.