I agree.

* vesting across 4 years, one year cliff: So the OP don't come here weeping next year because they got a moron that now has a big chunk of the company.

* Equal to all other founders: So the technical cofounder don't come here weeping next year because after building all the company was fired and only got a bag of peanuts.

@OP: Some additional questions: Do you have clients? Do you have a working prototype? What happened to the person that build it? Is the new cofounder going to get salary? Do the other cofounder get salary now? Are they full time cofounders or still have another job?

This. Most of the value of the company is to be created in the future, and you'll likely pivot (based on statistics, your specific idea may turn out to be spot on).