Hory, I dive a Pioneer as well, and the bungee does come standard with it. Where did you purchase your Pioneer?
Anyway, there is no problem dumping from the inflator hose even while bungeed as long as you know how.
Using the inflator or lower dump while horizontal requires you to roll right... if using the inflator, raise it above your head then dump. If using the pull dump, just raise your butt a bit, then tug the string.
On a vertical heads-up (parachute style) descent, you have to lean back a bit from a perfectly vertical position, then raise the inflator above your head before dumping.
On a vertical heads-down descent, just tug the lower pull-dump.
I've found that using the lower pull dump in most cases is the best and most effective way to dump air.... even while ascending... you just raise your butt and dump