Anons, I have figured out how to install mods for DS1R in Addition to seamless Co-op.
you need your mod (i picked age of sunlight, seems fun!) then you need DS1R Seamless Co-op and Mod Engine 2 (specifically the ds1r version, its on nexus)
set things up like this and stuff. oh yes and if you use age of sunlight all classes besides 1 start with 0 Resistance.. I think you need to level it to 1 or something doesn't work right kek