Javeline ammo delivery is some really awfull ability. Honestly during last rotation pubs were full of Javs that run out off ammo because her self-supporting capabilities are awful.
Supporting team mates isn't very good too. You got to be in her range a bit to start taking ammo and than get 0.5 mag a second up to 10 seconds (with Spares). That's quite a lot.
Now here is the thing i wonder:
Her ammo back back is attached to Vassili's and Aura's magasines. So why not make her pump bullets directly at them?
Lets say, make ability activatable with 10 sec duration and 20 sec cool down. Make her add 0.33-0.5 mag/sec into your magasine and another 0.5-0.66 mag to your total ammo. If mag is full you'd get 1 mag/sec to total ammo.