So, what do I need to know about adding such an optic? Seems like there are options anywhere from $10 to $200.
Is this viable, and is it just a matter of measuring the front sight and then using a micrometer to properly install the rear sight to an appropriate height?
Its done all the time ( making or adapting custom sights)
Viable OTOH depends on the skills and resources you have to make a mount for the rail and adapt the sight of choice to it.
What to know to design any sight for any weapon is as follows:
Mechanical sights are line of sight between the eye level and the target so you need 2 points- the eye height and the aim point.
If you already have sights- set the elevator to mid point and measure centers from front to rear then to where the eye would be and do your trig out to 100 m ( which almost all standard sights are set to) ( someone already decided the rest)
If you had to do both- determine if you go with bore sight or impact sight at whatever range you want your median at ( that's what didn't happen in the example above because someone already did it)
This will make you decide on "point blank" because if sighted in to bore then the barrel is horizontal to the datum and the sight line will be tangent
If you sight on impact the barrel will be tangent ( thus the rise and fall of the bullet) and the sight will be straight to datum ( that's not always the case depending on the caliber, bullet and sighting range if starting from zero)
Since there are already sights- all that has done so you will be safe cloning it with a few thou difference on the other end of the receiver providing you have the facilities to make the rail adapter.