What's wrong with reinventing wheels, he asks? Absolutely nothing. If.

If you have properly and fully evaluated existing solutions. If you have discussed with others experienced in the field what needs you believe these solutions are not meeting. If you have confirmed that they do, indeed, fail to meet those needs. And if you can add new features without introducing new bugs to make your better wheel.

With real wheels, each progression you stated was most likely made in a similar fashion: existing wheels were evaluated and found wanting. And then were tweaked into something new. Don't forget to do likewise here.

Now, if you were trying to do this as a way to learn how such templating systems are developed, go ahead. That's done in many other areas as well, not just software. But, here as much as anywhere else, when your learning is done, you're best to work with off-the-shelf standardised tools when you want to get real work done instead of reinventing what is already out there.