Remember, the amp rating of the battery is how long it will supply that level of power. So a 7 ah will provide 7 amps for 1 hour.
I ran a 7 ah battery in my 77 all summer long with no change to the electrics. You do not have to change electrics. No matter what battery you use, if your bike does not supply enough power to operate, it will always go dead. Sure if you do nothing but idle, it will slowly go dead but all a bigger battery will do is prolong that. If you are sitting in traffic that long, then you either need a motorcycle that constantly charges, find a different route home, or take a car.