Normally you would not have an Orion XS and a BMS CL 12/100 at the same time because you are putting 2 alternator controllers in series with each other. You could put a 125A fuse in the BMS so that it did not provide any regulation as the Orion would limit to 50A max. I am still not 100% sure if they would work together or not. Normally you connect direct from your starter battery to the BMS alternator terminal. If your alternator voltage is too low the BMS does not charge as well so the Orion will boost the voltage.
Your connection scheme will work, put a 125A fuse in the BMS, but I can not guarantee perfect charge control.
As you have an Orion XS, consider another alternative.
Orion XS
In = linked to + from alternator/started battery
Out = linked battery+
GND = to ground/chassis
Remote terminal connected to BMS ATC
BMS CL 12/100
BMS cables x2 = linked to battery
Alternator / start battery = not connected
LI-ION+ = linked to fuse box
BMS ATC connected to Orion remote terminal
Battery
Positive = linked to LI-ION+ and Orion+
Negative = to ground/chassis
BMS cables x2 = linked to BMS
In this case, the BMS is only providing safety control, no alternator charge control. All charge control is by the Orion. For safety the ATC on the BMS must shut down the Orion so needs wiring to the remote terminals. I do not know exactly how to do this, you may need a remote inverting or non inverting on/off cable, look in the Orion or BMS manuals.
