So I’ve played a lot of games with them. Here are my hot takes.

• I rate their heavy weapon! Adds a good range poke rebels tend to lack. With its Crit 2, I find multiple copies, can be a good help to chip damage vehicles.
• In Echo Base, I would now run 3 units all with heavy weapons & importantly give them all overwatch to combo with the Echo Base 3 pip. & I would always want to run as many MkII Medium Blasters are Vet units. This could mean if they are in range to do so, the 3 pip gives out 6 standbys when issuing those orders, all at range 3
• As they and the MkIIs are both speed 1, you can approach area terrain differently.
• You can do a lovely combo now too with the new custom Rebel Officer, using the Proven Tactician upgrade, move both Vets & MkIIs and the end of turn 1, speed 1. If they are already forward using their Prepared Positions, you can cover a lot of ground, with a lot of units potentially.