Yeah, filling it would suck. There are some REALLY nice units available for mounting in the engine bay that don't clutter up your firewall. I just wonder how big of a nightmare it will be to service under the dash. Clutch and brake systems both being hidden would be cool and look great though. Are you going to race the car? If you do, I would check rules about having fluids in the passenger compartment like that. It would suck to not get past tech after all that hard work. I would think with the right master cyl and nice plumbing, you could make the whole set up a really nice part of the engine bay and it would just add to the quality of your build. Just my .02