well if its not there then it doesn't exist.. support squads are already incredibly overpowered, they don't need to also hit on 2+s.
There should be a rule for HWs to get a plus to hit, and I'm afraid I disagree with support squads being overpowered.
First, if you look at other units like attack walkers, support bikes, tanks, or titans, and see what they can do, support squads are not overpowered.
Next, all heavy weapon systems come with some sort of targeting, such as tracers, scopes, or a laser-guided paint/fire/can't miss system, and HW troops are given additional training. Governments spend a lot of money on these systems, so they do all they can to make sure they hit when used. So HWs should get quality plus one for hitting. Indeed, a solid argument could be made for all technological armies, which would not include orcs or cults, should fire heavy weapons at 2+, because that's what they are designed to do!
The thing that made me ask this question in the first place was surprise. I've been playing wargames for 40+ years, and this is the only sci-fi based system that I've seen that doesn't have some sort of option for adding some kind of targeting plus to HWs, because, again, that's just what they do! So, given my experience, I believed that there had to be a rule somewhere for giving support squads a plus to hit that I just wasn't finding.
I doubt that OPR will change any rules because of this, but my humble 2c opinion is that it is something I think should be added.
Support squads are hilariously overpowered. there is no reason to take any other infantry squads for some lists, at the moment. Flamers and Fusion Rifles are incredibly broken. Veteran stuff is actually being removed from some lists entirely.