Other than the time taken to form up, formations are only as slow as their slowest unit.
In order to effect a movement bonus, the formation code would need to handle applying, and removing, buffs - to all the units involved - a costly process, especially in light of how often the formation code is called.
This also seems open to abuse.
"Always move your fatboy in a formation with 12 labs"
"Your ACU can run away faster when it is in a formation with 2 other tanks"
etc.
Also in general I don't think the game would be improved by people using formations more often. Formation move is mostly just used by people who want their armies to look cool. As in, the kind of people who have cool-looking templates for their bases instead of just making what it needed. There's no point in trying to balance the game for those people.
@Jip has been working on a change to formation mechanics that should make them far easier to use. I don't know how close it is it to release
@arma473 yeah, right now the formations are only used by people who want to look good, And this is because currently formations are a disadvantage thanks to their slowness, but if all units in a formation are given a speed bonus then people will no longer will use them as a purely aesthetic whim, but now they can be used to advance fluidly in conjunction with your shields, making them useful again.
You just kinda ignored his whole thing about you introducing new esoteric game mechanics in your solution to making this thing work
The issue isn't with unit speed per se. You'd expect units in formation to move at the speed of the slowest unit It's with how they all backtrack to form up, and the pathfinding in forged alliance is so poor which basically causes a mess. Also formations at waypoints frequently stop and never get started again. Presumably this happens because units within the formation are not able to reach their final positions at each waypoint (due to terrain) and as a consequence never initiate the move to the next waypoint.
@reckless_charger Iād guess those are the things Jip is working on in his formation rework, but would be curious to hear from him on that.
The solution is most certainly not to give the slowest units in a formation a speed boost
I'll come with detailed information about what I've found, working on and fixing in a week or so 
. For those interested, you can get a peek here:
A work of art is never finished, merely abandoned
The movement speed while in formation is fine, it is the time it takes units to get into formation in the first place that is the problem, and also when they get pushed out of formation by terrain like cliffs.
I would recommend a system where the movement speed bonus is only applied while the group of units are getting into formation, or getting back into formation after being dislodged by terrain, and only to the units that are not currently in position in the forming formation. Then, once in formation, it goes back to the standard of the entire formation only moving as fast as the slowest unit. This would fix the biggest issue with formations, in that they take so long to form.
One method to prevent unintended abuse is that a cooldown could be applied to each unit for this movement speed buff, where they cannot receive it for 1 minute after previously getting buffed.
I know it would be a lot more complicated to implement properly, especially making sure that it can't be abused as people can be very creative, for example the commander may need to be excluded from this formation buff, but I am just giving my thoughts and ideas that attempt to satisfy both the wants and concerns of both sides of the conversation I have seen here.
Reading through this: https://github.com/FAForever/fa/pull/5908 it seems like a lot of the issues are down to path finding, but I still think a system of movement speed buffs while getting into formation would help regardless of whether these path finding issues are fixed.
