I'm currently building what you are looking for actually. I'm doing a ground up resto on my R90 but with all modern electronics. Got a brand new harness, 450w charging system, new modern started, electronic ignition, LED tail light and turn signals etc. Also, the rear shocks will be new Ohlins and the front springs will be progressive. So I think that is about as modern as you can get on this bike without swapping the gauges for a modern R bikes...which I've HIGHLY considered and will take suggestions/advice towards that in my thread below
The whole idea of me restoring my r90 was if BMW remade an old model today, what would it be like. Granted, this resto wont be together until march and I'll be riding it and slapping more parts on it through the year.
Here's the thread in progress: