Not hard at all. Something I have learned from power plant operations is that "pressures" are more important than "temperatures". A drastic change in pressure will tell you that there is a definite problem and will be accompanied by a change a temperature but a change in temperature will not always mean something is broke or wrong. These of course are generalities but IMO if you are gonna monitor something all the time (like with a stand alone gauge) and only have a limited amount of space then I believe it should be a pressure parameter over a temperature parameter. I know EGT's are important but they dont need to be monitored all of the time IMO. You can do it when you are towing, racing, or trouble shooting and the CTS can be expanded to monitor these from 0-2000F. Especially since you can montior whatever temperature you want to with the CTS.
If I were running stand alone gauges, I would fuel pressure, actual engine oil pressure, boost pressure, exhaust back pressure, coolant pressure, etc. The list could go on to include transmission line pressure, high pressure oil pressure (injection control pressure), and actual cylinder pressures. Sure this might be over kill but it would definitely tell you that something is wrong if one of these flucuated significantly. Again these are just my opinions and hope it helps. Best of luck with the build, sounds good so far.