The manufacturer's family is just a hard 90degree plastic elbow, that is hard plastic. I'm more thinking of a family that would allow you to model the bend in the pipe more accurately. It isn't an elbow in reality, as much as a bend your making in the pipe as you model it. It is an elbow in Revit, but in reality it's just bending the flexible pipe. So for example, for the bend for the stub out of the wall, this is often done with a plastic guide that makes a 3inch radius bend in the pipe, and uses a plastic guide to prevent over bending and kinking of the line.
The 3inch radius is generally considered the tightest bend you want to make in the mainline 1/2" pipe in a run. But maybe in another case you'll just do a 12" bend. I thought this family would be more easily made, but I'm running into some issue. The attached family was where I started, but I've got two outstanding issues that seem to be holding me back.
(1) how to make the family match the angle of entry. Right now it is modeled around a 90 degree, but ideally you could make that any angle kind of thing.
(2) I'm not exactly sure how to make the Pipe Diameter reference the diameter of the pipe it is connected to.
But if we could get this to work it would allow you to more easily treat the mainline run of the water supply line the flexible line that PEX actually is. Whereas the Flexpipe tool is too clusty to work with, this would go a long what to making the straight piping tool more accurate for modelling piping like PEX.