Can I add a blind spot monitoring system as good as a factory system?
Probably not, why not just trade for a vehicle with the systems you want.
Definitely not. The add-on system suppliers don’t have the capabilities to engineer a system as good as the factory can.
Being curious and knowing how to use Google I found an article by Consumer Reports. They bought a Blind Spot system and it took their master mechanic almost 4 hours to install . They said it worked but it also had some very annoying features .