I have done a couple of STI's like what you want to do. I used the Cheely mount with a Delta Point pro. Drilled the rear sight slot for the ball inserts so my friend could change from a slide racker to the rear sight when he took off the mount. On the Delta point it has provisions to add a cowitness sight so we added that. He also went with a BarSto comp barrel. This really made a nice set up. The comp barrel only helps a fraction of what a full comp does but it does help. i also did the same above to a STI Maurader and added the Cheely steel grip and EGW fire control components. This made for one fine shooter. That added weight in the grip does wonders. If you want a couple of pictures email me at firstname.lastname@example.org.
I have a Marauder I decided to play with like you are wanting to do. I started by replacing the whole fire control with EGW, CK Arms SS grip, drilled and tapped the frame for a CK arms DP Pro red dot mount, DP-pro red dot, Wilson Combat multi comp.. I took and really lapped in the fit of the slide to the frame for fit. Each step took a little bit of work and fun time but it made a sweet shooting gun for 9mm minor. The dot has very little movement! This isn't for everyone but while costly it was fun for a retired guy and shows what can really be accomplished.