First note - this army will almost certainly go against orks (very small possibility of allied chaos marines, but with a new ork codex out I suspect he'll be kicking the tires of the new 'dex initially) and low chance of any fliers (and to be honest I'm more or less planning on ignoring any ork fliers that show up - historically it has been boyz in trukks (or bikers) that kill me).
Hey mate, here's my thoughts:
Company Command Squad
Veteran heavy weapon team with lascannon
master of ordinance
This should be solid against an ork list, the lascannon is really your punch in case he likes taking deffdreads or meganobs, because BS4 and the wealth of possible orders can mean that this one shot can make a difference. I almost never have success with the MOO BUT when I do, it is always worth it. Target his heaviest vehicle, especially if it is central or in proximity to either footsloggers or a clump of other vehicles - the 2D6 pick the highest, side armour striking barrage at s10 will do you wonders.
Commissar - Very yes. Combine the squads of one platoon and stick him in there, to form a group that will hold fast when the orks do crash into them.
Platoon Command Squad
Flamers work best when you get close to the enemy without being charged the turn before (although the overwatch boost is nice) and my guard, not deepstriking, seem to have trouble doing that. Unsure how you want to use these guys, but I would personally go for a missile launcher (for flexibility - can kill trucks and troops) and two snipers to precision shot nobs with power klaws whilst there are still a bunch of boyz in the enemy mob. Chimera is optional, keeps them alive and issuing orders when the time comes to first rank, second rank, but I'd otherwise stick them up the back of a combined squad and spend the points on an aegis line or similar (only because i'm not getting such a mech feel from your list)
3 x infantry squad with mortar team, grenade launcher, vox caster
Awesome, combine the squad, stick them around your tanks in as much cover as you can, throw in the commissar and keep the platoon command squad handy to give them the extra shots.
heavy weapon squad with 3x lascannons
I play these from time to time and honestly hate them. It may just be my rolling, but 4s to hit doesn't sink ships or drop trukks fast enough. I'd switch to either Heavy Bolters for the extra points or autocannons for the extra anti-armour shot. Missile Launchers may also do the trick.
Platoon Command Squad
Same as before, unless you want to use this one out of your two PCS as your 'reaction force' who either wait in reserve (with the platoon... a gamble to sacrifice firepower for turn one, unless you tack the second HWS onto the first platoon) or in cover before screaming out at top speed to deny or take an objective, flank a mob who is too close to you or save the day by taking a bullet for your warlord.
3 x infantry squad with vox caster and grenade launcher
Unless you want to keep these guys separate for objective purposes, I'd combine these guys and take a wall of martyr's defence line for cover save and stubborn special rule. They become the forward most unit, and the intent is for them to die bravely delaying the enemy advance. If they survive, great! take an objective. Note - don't give these guys an objective to hold, because the point of them is to let you hold on to ones further back)
heavy weapon squad with 3x autocannon
Definitely rate autocannons, they can do wonders for an approaching light vehicle squadron.
Lehman Russ squadron - 2 x LRBT with lascannon
F Yeah. My LR support team of choice. You may consider dropping the lascannon for a HB since you can only snapshoot after firing the battlecannon, plus extra shots. Also consider swapping in one Demolisher to put the finger up at those incoming mobs of boyz and nobz just before (or after?) they crash into your lines.
Haven't tested these yet, but they look like they are made of win, as they say.
Beloved as this unit is, in this scenario it is probably worth retiring the lone basilisk. It hurts when it hits, true, but then it's out of action by turn 3 due to minimum range or enemy action. Consider instead taking a manticore - up to three times the destruction, who cares about losing one AP when fighting orks, and if he's still alive after your fourth shot then you have a perfect back objective holder.
Hope you find this advice useful, really interested to hear your experiences and feedback.