That will work if you just use a random IR code from whatever product, then learn that code from remote into your control processor. I don't see any issues with this.

As cheesehead stated, you need rp6 to do any serial control. Keep in mind you need rm433 since the rp6 doesn't include rf antenna.

Were you understanding the software when the dealer showed it to you? If so, you might just go with this dealer. If not, I would recommend looking elsewhere based on your comment that you believed you knew more about line than him. I guess it is possible he misunderstood what you were trying to do, but it seems fairly simple to me. You are really using the RTI remote for very basic functions, not even getting close to its capabilities.