Can any aircraft have ETOPS?
Theoretically anything can be certified if resources are allocated to meet certification requirements. It may not be practical though:


The plane must have at least two engines (obviously)
It must have the range to fly to an alternate on one engine only
Engine failure should not increase cockpit workload too much. Mostly this means some automation system that can operate with asymmetrical thrust.


(2) rules out small twin-engine planes that only have a few hours of endurance on a full tank, and (3) rules out anything without a glass cockpit and avionics suite.

Also, ETOPS is not just about aircraft design; it deals with aircraft maintenance as well. The manufacturer and operator need to come up with a maintenance program that reduces in-flight failures by monitoring various metrics and taking preventive actions before a component fault happens.

Therefore, on some aircrafts, it may not be worth the effort to obtain ETOPS.