I had one of those Kabar gun bayonets, while they were on sale for $15.
Knife quality was good, fitting system not so good but, overall... It was one of the most dangerous attachment I've ever put on a gun.
I quickly got rid of it.
It's just like you're begging to puncture yourself or chop your own finger.
While it was looking good on the gun, it was indeed a terrible idea.
And if you put a folder up front... the opening of the blade might be an issue with a regular system, and bulky with an OTF.