You have opened several issues.
Are simply badly designed.
These reckon units need a better design where they should be support unit relying on utility having low Pop so that they can fit into to an army composition but not substitute mainline infatry.
I do agree Pathfinder is badly designed. JLI & pathfinder shouldn't have existed. insta kill is too powerful mechanism in the hands of moral. I bet BT never dreamed of 4 barfinder spamming.
They come with 2/3 elite carbines that are very good close range and 2/1 scoped carbine that are good long range. This weapon should not be mixed. They should have only long range weapon so they become vulnerable at close range.
I think that's intended nerf on pathfinder. carbine(elite or not) don't do serious dmg in my experiences in mid-long range where most of the combat for the pathfinder happens.
The critical kill mechanism need a redesign since it become silly in unit that can be spammed. One could try making the scoped carbine an upgrade (similar to JLI) and the critical kill a timed ability for all jli also (maybe with mu cost).
There XP value is too low and they gain veterancy too fast.
The beacon is a nobrainer ability that needs a better design.
2) Forward reinforcement/heal points
FRHP including ambulance in my opinion are available too early and too strong and they are one of the main reason why camping has become a good strategy.
I read some post claiming that flanking is difficult due to maps design but imo FRHP point contribute much more to the issue.
Imo one could try a number of solution like reduce healing auras and adding a reinforcement speed penalty when used outside base.
Some of these unit could see further changes. For instance Opel truck fuel cost remove but now can heal only in base and passenger, Bunker can not be use both upgrades but command bunker heal occupants (maybe create medic kits).
AFAIK, they already nerfed reinforcement time for the forward reinforcement (after major setup etc). Kinda not sure why this topic has been brought up. It seems fine in 1v1 or 2v2 anyway. Not sure about 3v3 or 4v4. But nowadays all faction does have one right?
And then there is the scott that is simply too difficult to kill. One should at least remove the defensive smoke from the unit.
One could also try two firing MODs one ballistic with long range but slow projectile suitable vs static targets and one direct fire but with sorter range.
This is a problem a continues buffing and can not be solved with more buffs. Actually things need to be slowed down instead of speed up and if there is a need for such a change it is the faction that need to be delayed and not the USF that need to be speed up.
After BT nerfed it's auto attack range to 50 - I say all is on the hands of player. If you want safe distance & precision, it requires a micro(barrage). auto attack isn't a big thing IMHO. All true power of the scott comes from the endless barrage which requires a lot of micro. And it does cost you a fortune for AI only unit. So... Just flank it with 1~2 P4 when you can.