Hi,
As a rule, I can’t say whether or not a future PR will be merged. The only way to know is to perform a review of that PR.
That said, your proposal seems like it may have trouble fitting the general “100 users” guideline as mentioned at Contributing to Klipper - Klipper documentation . In general, we try to keep the main Klipper repo geared towards mainstream hardware.
As mentioned previously, an alternative solution that would not have long-term software maintenance concerns would be to deploy an mcu instead of an i2c expander.
Separately, the mechaduino branch I wrote a few years back has code for supporting typical H-Bridge style chips - Mechaduino experiment .
Cheers,
-Kevin