The idea of jit compilation of a web server in a small project is pretty terrifying to me. The attack surface here is enormous.

And for what? My back end on a single host isn't pumping at 35k qps. If each request is 500 bytes, 35k qps is nearly 20mbps sustained with zero other io (in each direction). And this is using only two threads!

I think you'd be hard pressed to find an application where this is meaningfully useful versus just scaling horizontally. On a box that can run many threads in parallel, Caddy still vastly exceeds my ability to respond to pretty much any useful traffic. It's optimizing for a metric that wasn't a bottleneck in the first place.