I would be perfectly all right if BG3 ended up closer to the 4e rules for disengagement and flanking. Would disengagement costing movement but forcing a character to take a movement penalty be a good compromise? Larian seems to feel that disengagement costing a full action is too harsh for a video game, but *some* cost is obviously correct.
Hmmm your disengage suggestion would be very similar to 3.5e/Pathfinder's 5-foot step and is certainly more realistic/immersive than Jumping. You could choose between: a.) moving away at full speed and provoke b.) backing away slowly and not get AoO'd but then you end up relatively close to the enemy. Mechanically, I suppose this version of disengage would halve or quarter your speed (min 5 feet).
However, it's not actually much less powerful than the current jump+disengage...it still gives party members the ability to ~freely (at cost of bonus action) move away from melee enemies. If you're trying to say that this slow disengagement doesn't cost a bonus action, then it's even more broken than what we currently have with Jump+Disengage.
My intent with the suggestion is to increase the cost from what it currently is, but not so far as to prevent characters from attacking, since I assume Larian chose to change the cost for video game adaptation reasons. So, yeah, bonus+movement penalty for disengaging, something that would get your character out of threat/AoO range but not much farther.
It might also keep enemies and PCs from circling around constantly and jumping about for backstabs; adjacency reducing your movement speed would mean it would be possible sometimes to get around for a backstab, but it would take more effort to do it.
In 4e, it’s a 5 foot shift, movement only (action economy was different there, no one got extra minor actions as class features, and if you shifted, that was *it*, no more moving on your turn), but it’s needed there because *any* movement adjacent in 4e that isn’t that 5 foot shift is going to get you smacked in retaliation, and *any* ranged attack adjacent will also provoke an AoO. That doesn’t seem to be the case anymore! Maybe it’s just me preferring my preferred edition
I can see why, playing BG3, that being able to move away that easily is an issue; threatening range just doesn’t feel particularly *threatening* when it is so easy to get out of it, nothing has any ‘sticky’ to it, but I can also appreciate why Larian might have chosen to make it so safely leaving threatened “squares” no longer removes the ability to attack.