You're talking about CPU, not memory, right? Because you can't burst above 200% of your memory.
Speculating about some other universe, they might be able to structure it that way, but would have to charge a lot of money for the guarantee when you used it.
What exactly was your svn problem on Capistrano?
BTW, one thing that happens when you switch to PS is that it becomes really obvious how much CPU and memory your account takes up. And when it becomes obvious to support that your site is eating a not-insignificant part of a server's resources, they are very hesitant to switch you back.
Dunno if it interests you, but support did mention to me that I could open two accounts - one PS and one non-PS, and allocate my sites between the two.
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