In any case, since 1000TPS is bandwidth limited, we dont really have any CPU bottleneck issues, unless you actually want to calculate crypto functions in the script instead of pushing it down with the script embedded in the AM
Each node (perhaps other than "light nodes") would have to *do* the crypto calculations as part of running the script otherwise once again you can just be tricked.
Again CPU may not be the main problem - but the size of the scripts would for sure be bigger than standard NXT txs are plus the VM "state" would also need to be stored somewhere (presumably as an AM - although currently that limits your persistent state to a paltry 1000 bytes).
I assumed, not every transaction would contain code to execute...