I think it's a great idea.

I like knowing what my turbo is doing - if it's overboosting/spiking - if it's underboosting, identifying vacc leaks by watching it at idle.

You can get small square guages that you can cut into a trim piece,

Automobile Multimeter Gauge FOR EGT Boost Amber LED | eBay


I have seen some really small digital displays that literally just the panel itself, no housing - they show a number ie. no needles or graphics etc. You could mount one of those somewhere inconspicuous. I have seen them BEHIND dash vents so that they're literally invisible except for when powered up and you just see a number display behind your vent. This guy has also mounted one inside his mirror by cutting out a window in the mirror film from the inside: