I don't think this is a good idea because REs have their own abilities and uses in the game as others pointed out.
The only time I see an issue is when you choose a commander that has specific RE upgrades like the flamethrower because it complicates the RE's combat role
The most efficient role for REs is as an AT squad w/ double zooks because the additional sweeper doesn't reduce the combat effectiveness of the squad vs. armoured vehicles and at vet 3 they get a fifth man to increase survive-ability.
This efficiency is increased when accounting for other squads that could have bazookas; LT and Captain have a Thompson, so a double BAR on those squads augments the close range DPS of their SMGs. Riflemen are expensive and have good anti-infantry DPS when upgraded. The Major has too little models to be an effective combat squad.
REs can take advantage of their volley fire ability when they're equipped with BAR(s)/M1919 but, again, you're better off putting those upgrades on your riflemen or other combat infantry squads like rangers or airborne.
With the flamethrower or the rifle grenade package, you're sacrificing DPS if you get zooks or a minesweeper so if you want 4x zooks on the field you're forced to either build an extra RE squad or put zooks on other squads that would be better off in an anti-infantry role.
Of course, the LT and Captain provide some utility with their smoke grenades disabling the main guns of enemy tanks if fired directly at them (but REs have this too), and the Captain's fire up ability can help get squads to a position faster to snare or fire more zooks. Perhaps on less open map the RE upgrades make them better for the flamethrower/rifle grenade package and you'd rather get zooks, but riflemen are just real good at mid range with upgrades. The only time you could get a better zook squad than REs is with the airborne support squad that gets the camo w/ the zook upgrade.
tl;dr REs are best at being an AT squad with zooks because of the attributes of the squad as well as the attributes of other squads in the USF faction.
Did I miss something in my argument here?
No, you did not miss any points.
I was just thinking about Rear Echelons more than other engineers since others have many role fulfillments.
The best designed engineers I must say in this game is Wehr Pio and SU Engineer because they have 2 clear distinctive roles, and some which they will recieve from the update soon.
1.- Mine Sweeper and the fact they fill the role of better repairs (soon with the upcoming update) and clearing mines.
2.- Flamethrower which is the best design, mainly used as a support and effectively used to throw away the bonuses the enemy recieves when behind cover and in buildings.
The next best Engineer and yet broken is UKF Royal Engineers. Can pretty much do anything up to fulfilling either the role of a AI supporter or AT unit.
Soon Sturmpio is getting some deserved changes, such as filling more a suitable scaling role in combat. Surely a change that makes it yet more viable.
But Rear Echelons, I am not so sure since they are not recieving much changes in order for them to be utilized more often.
Here is a different idea:
What if Rear Echelons can acquire themselves with either the Bars and Bazookas already in the beginning without weapon tech.
The tech for "unlocking weapon racks" is meant only for other classes. The unlocking purchase should be purposely used as for mid-late game scale and increased infantry superiorty. The tech locks purposely any other form of USF infantry except Rear Echelons only.
Rear Echelons should be able acquire them early ignoring/without the need to tech.
Since the timing of most other mobile infantry ATs are accessible more early without much cost, the fact that is not a great AI unit, it is more designed a supportive unit role.
Another interesting thing would be also, if Rear Echelons could acquire Bars early too but instead they will recieve a 30-40% discount on Bars only.
In this way, to improve support and for a more effective use with "Surpressive Fire" since it only get better the more useful the weapons are!
This would definitely be a better change in order to make Rear Echelons, in this way, more popular.