Looks good. My thoughts are that the MAX9926 can theoretically take any input, including coil (-) and magneto if the shunt is in, making the opto or other alternative circuits unnecessary. Chips such as the LM1815 cannot take square waves well, and other circuits cannot take VR well, but the MAX seems to be able to do them all with its added brain power. My thinking is to prove real-world function in all these modes, and designate it as the "standard" input, with jumper setup instructions for common configurations. Sort-of a "If you're not sure or may change, use this, and do that." Then, list other specific input alternatives as exactly that, on an alternative inputs page. Provide direct links to schematics and BOMs on each.