Enjoy paying support costs for having those archers outside your borders shooting barbarians.
Unless they're inside your borders, in which case enjoy being pillaged while you shoot instead of killing them
It's far less of a magical ticket to lv6 than it used to be, thanks to the recent soft cap. The main reason it exists is to make it worthwhile to use archers as dedicated ranged attackers. They have low attack strength, and continue to have low attack strength for the whole game. So they're pretty much deprived of the "Double xp for Winning on the Offensive" that melee units can take advantage of. And there's a thread in the FFH strategy forums which pretty much mathematically proves that archers are almost useless. They're a lot better in FF because of ranged attacks, and the ability to level up from it, and it's less of a "swarm axemen at all costs" game as a result.
Also consider that the archery promotions have no direct combat benefits. This is an opportunity cost, meaning that while your archers get better at shooting things, they
don't get better at defending the stack. Without those archery promos, gaining significant levels through shooting stuff takes a LOOOOOOOONG time.
The only thing that's really magical about sixth level is the sidar shading. And upgrading to immortal, I guess, but can archery units even do the latter?
If getting shades as Sidar is too easy, perhaps that needs to be rebalanced for FF ? FF also has the passive xp buildings, xp boosting promos from commanders, and decimal xp accounted for. These things make levelling up in general easier than FFH. So if an FFh feature is too easy to take advantage of because of them, then that feature is what needs to be considered for rebalancing, not reverting things to make us more like FFH.