Does it make sense to simply model in blender units? My thinking is if I model in blender units and just think of them as inches, feet, mm etc. Now if I want to append a "blender unit" object into a scene that I consider in inches, can I measure a length on the appended object and simply scale that object by a multiplier to make it match the proportion of the scene that I need? Would this work?
Blender units are actually metric.
One blender unit is 1m.
Of course you can disregard that, and model however you want, but when it comes to dealing with light falloff and depth of field in cycles or physics or fluids and cloth and other simulations, the calculations are done using blender (metric) units. In other words blender is trying to simulate those things based on dimensions, light energy and other forces in the real world.
For things to work as the tools are designed, it is recommended to make the objects as their real size would be in the real world.
Note that you can set the units (in the scene settings) to be in the scale you need: metric or imperial
and within those settings you can choose to work in cm, mm by changing the scale
You can also change the scale on the viewport to make the manipulation of the geometry easier when working with very small or very large objects.