I think the Nuka-Cola machines in the wasteland need a use. The ones in random encounters might possibly have one or two in them after all these years, but even that's a stretch. After using repair on them, you should have a roll to see if you get a nuka cola for free.
The ones in town could be done differently. It seems that someone in the wasteland knows how to make nuka-cola. Either that or the guy in Junktown raided a NC factory and has a huge stockpile. But I think the machines in towns could be full of them, costing only 5 or so caps per bottle. Thieves could have a chance to do something here. With a successful steal roll, the thief would get the money in the machine as well as some free nuka colas. A failed roll would result in guards responding like a normal theft.
As for the machine in the themepark, this option would remove any necessity for it. What I suggest, despite the flaming i'll get for mentioning F3, is that it makes Nuka-Cola Quantum. It gives the same AP boost, but also restores some health and provides very minor radiation.
