Most stock VQ35DEs from 2003-2005 dyno'ed out around 235-245. Stock with full interior everything they ran on average about 13.5 -13.6 1/4 mile. I think officially the stock 300ZX's 1/4 time averaged just a little bit higher in the high 13s to 14 even. The stock 300ZX came in around 3300 lbs vs. the 350Z at around 3300-3500 depending on trim. They were very close performance wise in stock trim. I think the 350Z had a slight edge.I'd be ok with a smaller lighter version and also a smaller N/A 6 cylinder of some kind. I'm with you on the 4 cylinder too. That is too far from the Z heritage. It would be a reborn 240sx, NOT a Z car.
You have to think of it from Nissan's perspective though. With each new generation, it should outperform the last one, at least that is what has historically happened with most sports cars. Thinking about that it's probably a fairly difficult move from a marketing perspective to make the car slower than the outgoing model. But wasn't that the case with the 350z? Didn't the 300ZX outperform it in just about every regard?