After thinking about it, I recognized why people see unlimited use as being a problem, and how simply giving it ammo or just damaging the line would still be a poor way to correct the issue, since it won't resolve other ways people will be able to abuse it.
Giving it ammo is easily resolved since it doesn't address the problems with continuous use of one shot, or the actual runs from base to base that lead straight to inventory stations, or that don't require the totality of the set amount of ammo. Players will just make "grappler stops" to replenish themselves and will be off to abuse the system all over again. If you do give it ammo, you'll have to add in other variables to enforce it, which negates the purpose altogether.
So, I keep my vote of "no ammo," however...
You may want to consider something new, like an "energy capacitor" for the weapon, one that doesn't use jet energy for fuel, so it behaves like a pack's source of energy. You'd start off with, say, 100 units of energy in your grappler. Firing off a shot depletes 25 units, which means after four repeated shots (with no swinging involved), you have no "ammo." Remaining on an active line would drain 10 units per second, for an example. So, realistically, just swinging repeatedly on line after line won't be possible after about three shots. Swinging on a single line would afford you with only about eight seconds of use. It would recharge at something like 10 units a second when not in use, so you'd have to use your jets actively.
All those variables can be changed, of course. I'm not in beta, so I don't know how the game feels firsthand, so the variables I made up are based on conjecture. It may need more "ammo" than I gave it. The idea is to give it a limiting factor without limiting its usefulness in the field, which is the concept behind the grappler.
Giving it ammo is easily resolved since it doesn't address the problems with continuous use of one shot, or the actual runs from base to base that lead straight to inventory stations, or that don't require the totality of the set amount of ammo. Players will just make "grappler stops" to replenish themselves and will be off to abuse the system all over again. If you do give it ammo, you'll have to add in other variables to enforce it, which negates the purpose altogether.
So, I keep my vote of "no ammo," however...
You may want to consider something new, like an "energy capacitor" for the weapon, one that doesn't use jet energy for fuel, so it behaves like a pack's source of energy. You'd start off with, say, 100 units of energy in your grappler. Firing off a shot depletes 25 units, which means after four repeated shots (with no swinging involved), you have no "ammo." Remaining on an active line would drain 10 units per second, for an example. So, realistically, just swinging repeatedly on line after line won't be possible after about three shots. Swinging on a single line would afford you with only about eight seconds of use. It would recharge at something like 10 units a second when not in use, so you'd have to use your jets actively.
All those variables can be changed, of course. I'm not in beta, so I don't know how the game feels firsthand, so the variables I made up are based on conjecture. It may need more "ammo" than I gave it. The idea is to give it a limiting factor without limiting its usefulness in the field, which is the concept behind the grappler.