Wanted to play Heretic in DOS with mouse look, so, in a way, revisited this old topic. Only this time aiming to achieve control changes with a TSR that uses id protocol for control devices, and not binary patching. I am not sure which project preceded this; the usual source of Doom engine games wisdom has example of driver source code for Doom, but for Heretic game source code is available, so I simply started from scratch.

So far so good, so sharing an "alpha" build. Source code is available with the moustest project in github and is a single file Watcom C project.

The "driver" interfaces built-in vanilla Heretic code, no code patching happens. If CuteMouse is loaded with mousewheel support (e.g. as CTMOUSE /O /3) mouse wheel is by default mapped to inventory browsing with middle click (usually "wheel click") bound to artifact use. Alternative modes are available that map wheel to weapon cycling or flight control, or use "wheel click" for "over the shoulder look" - see CUTEHT /?.
Also "autorun" can be activated as an option.
In all modes LMB controls shooting, RMB is for strafing and RMB double click is use (switches, doors).
If you are curious, I am testing it with a PS/2 Intellimouse.

The most user-friendly way to run Heretic with the TSR is by providing arguments as a response file and letting CUTEHT filter it via stream redirection (again CUTEHT /? gives an example of this).
It is advised to suppress Heretic's own mouse support code as it may interfere with TSR's usage of int 33H, and the example does exactly that.

Here's a brief capture from an emulator of the TSR "in action".