I don't see how it would help in that particular situation. it'd just be the same thing, except they're moving slower
I don't think you understand, but that's probably my fault. Essentially this means that sneaking up on players is a garuntee of a kill pretty much because your target becomes slowed and loses their jumping ability entirely, meaning that players have to use cover built into the maps more effectively instead of rushing in ahead and jumping around.
Counter strikes core gunplay is based on this concept. Dispite having a high base speed and jumping ability it is often better to avoid close combat on an enemy that is aware of you by closing in. If you've played counterstrike you know what this is, and you'll also understand why it is a different style of game to an arena shooter, which is what blockland boils down to. Considering most gunpacks nowadays are built around non arena type gameplay what with reloading and recoil, I think it's time something was added to make these weapons more viable instead of feeling like stuffty cod guns in quake.
I can think of 2 games that I've played that have this concept, one being the uncharted 3 mp and the other being counterstrike. There is probably more. A simple thing like this allows for radically different gunplay, and I think that's cool. This would really help with making weaponpacks like T+t and hk and bkt and gravity cats stuff feel wayyy better, and it's really all those gunpacks ever needed.