That sounds feasable.

With an "optical" link as you have presented you would avoid any voltage conflicts.

I would test the blaster output for voltage measurements to see if you could just hard wire the IR input like you would an IR receiver to the signal in and ground terminals.

That reminds me... I need to really take a close look at the dynamics and properties of the RTI signal transfer in and out of the RM433s, keypads and Processor ports. I realized the other day (see my recent post on standalone systems) that I do not actually know the electrical properties in this regard... I have always just assumed and made decisions based on practical applications and info from others as they relate to those assumptions.