@AJP that dash pod does look stuck on and not my taste but could be used as a base to attach the top of the VW part on. Everything else is already done so easier to do.
The easiest way to have a display as you suggest is to bin the RNS (I don't think that can be made to display anything other than it already does) and install an iPad. These guys - https://instagram.com/p/BGP9O__lcYT/ do excellent work and have done many installs with iPads. Get a blue tooth OBD2 scanner and a suitable app then have all the info displayed on the screen as well as nav, iTunes, angry birds etc. I think the app a lot of people use is called torque pro but not 100%. Info won't go through the MFD though to my knowledge
You've got my brain ticking away with that idea. Certainly an alternative to Polar FIS if there's an app that displays the same data as accurately. And moreso for me, I'm looking to upgrade the headunit at some point. Two birds one stone. I'd guess that for someone who already has an RNS510 or decent HU the better option is Polar, and a traditional boost gauge if needed. But for me... I really like the idea.
Regarding Polar, I do have Highline, but no multifunction wheel, so if I was to go for Polar FIS instead for whatever reason would I still have full access to its functions? Either way, the option you suggested with the ipad sounds better - for my needs at least. I actually saw a few screenshots of the Torque Pro display when I was googling things earlier. Looks decent.
If an ipad also functions well with a decent speaker/amp/sub setup it could be a winner. As much as I like the idea of gauges on the screen, I still like my tunes, and sound quality. Maybe if the ipad outputs to a processor before the amp that could work.
Hmmmm. Lots of research ensues. Need to sort out some greasy nuts and bolts before I get that far though. I've no choice but to make this a long term project!