Unfortunately we didn't get any input for combined power adders when the rules up for suggestions so it was let alone and now they are set for the year but it can definitely be looked at for next year. Agreed, the spool thing can be an issue for 6's with the larger turbos and tight converters. If it gets allowed, it will be spool or down the track since you can't control the use once it is plumbed. The only control would be the size of the bottle since you can get bottles as small as the ones paint ball guns use.
If you can talk a good enough game, you may be able to work something out with the guy your running against so you can get the time you need to spool it at the light without the juice. Maybe next year you won't have to be so nice.....