Read the thread on modifying a 1500 to fuel injection and as AZgl1800 mentions it was reported as working but not just right. Lots of threads on converting 1000/1100/1200 engines to FI but it is a labour of love not economy. A lot of people start, some finish some don't. It is recommended that if you do venture down this path, you separate the FI aspect into two phases. Take on the the fuel management or the ignition timing, but not both at once.
I have an '85 Limited Edition FI model and I'm investigating the possibility of replacing the ECU with an aftermarket unit. There are the Microsquirt family of products, and the Speeduino project (uses Arduino components) - may be others. A lot of car enthusiasts use these and are very successful. The issue I have with the '85 is the CFI system, Travel Computer, and dash are all interrelated so the trick is to duplicate the existing system.
There are a lot of component specs needed to make an aftermarket ECU work and these specs are not readily available. Lots of upfront legwork required.
If it's a retirement project and you have a second bike to ride, go for it. If not, keep the 1500 as is. I prefer FI over carbs, but the 1500 is fitting in nicely.
There are several 4 cylinder fuel injection projects on the Naked Goldwing Site. Most use the GL1200 intake and injectors and the Microsquirt system. Of course if you went to all that trouble why not put a supercharger on it for good measure?