Would you have interest in participating in a Ninja 250 Spec Race series?
Absolutely.

Would you buy/build a Ninja 250?
Depending on how quickly I become hooked.

Would you rent a Ninja 250 if it cost only $200 - $300 per weekend? (That's less than most of you spend on tires, by the way...)
Yes, especially as a means to determine if it would be something I would want to proceed more aggressively with.

Would it be an additional race to your current program, or would it replace you current steed?
As of now, an addition to classes I am currently running.