The reason Archer causes immobilisation is that at certain impulse values, units become "unglued" from the ground. In Spring, for ground units, this means they can no longer move under their own power.
This is a binary condition: units can either slide and be thrown, or they can move at their own power, never both.
I'm now thinking that maybe it's possible to replace Archer's impulse push with an inertialess push. Something that displaces the units it fires at, but doesn't give them energy, so they can still move as normal.
This is not something that's applicable for Newton/Jugglenaut gravity weapons, because throwing things is very much part of their design. But Archer is not a gravity weapon: it deals direct damage (with AoE no less...) and only has a push mode.
