1) people who want to "buy a VISA" (aka have the money to invest in a new business already) wouldn't need any new legislation. the existing EB-5 handles this.
2) VCs have no specific control over entrepreneurs ability to qualify / remain in the US, however the entrepreneur is initially required to get at least one sponsoring US entity (VC or qualifying angel) to support the application and invest at least $100K. for renewal, they would have to qualify either by reaching profitability at a $1M revenue run rate, creating a minimum of 5 US jobs, or achieving a subsequent round of financing of at least $1M. True there are a few edge cases which might not qualify, however we're doing the best we can to draft legislation which is reasonable in most cases. (creating 5 US jobs in 2 years is a fairly low bar, which should be substantially easier than getting to break-even on at least $1M revenue, or raising subsequent capital).
3) it is not my understanding that creation of this new class will put substantial hardship on processing other types of visas, altho obviously the cost in time & resources is non-zero. that said, since most of the rqmts for the application process in this new visa class are market-based, not based on bureaucratic review, we expect to have a faster processing time than for other types of visas (and hopefully would not slow down existing visa processing much if at all).
for more info, please see http://StartupVisa.com