Was just flicking through and noticed what your doing, sounds quite cool

What I will say I have noticed is for the most part all temperature gauges made by VDO seem to be calibrated the same, on my baywindow camper I am using an oil temp gauge as a water temp gauge, I also had a porsche 944 fuel/water/lights gauge and with my bus up to temp the porsche gauge read the same as the oil temp, the fuel gauge read about the same as the the original baywindow bus one.
The only thing you will need to look out for will be the fact that you can get 5bar and 10bar oil pressure gauges, they have to be used with the correct pressure sender.
If using in serious application I would steer clear of the cheap rice look gauges found on ebay, while they look pretty good and are an indicator of sorts I found the oil pressure ones to be rubbish! Really inaccurate.
I think if I were you I would look for VDO gauges/senders on ebay/junk yards or autometer stuff, tried and tested.
I am putting a Golf GTi motor in a beetle myself, with that I will probably run oil pressure/water temp/oil temp(as my oil cooler will be seperate not part of the main coolant system). If your 1.5NA is stock then why have more than the original golf did gauges wise? stock beetle speedo will tell you what you need to know in the way of lights/fuel/speed, then unlike an aircooled you just need to keep an eye on your water temp. Thats all I have as unless your higher end of performance, why have too many 'worry' gauges? Do you really need to monitor your EGTs? if its a stock motor vw didnt fit a mk1 golf with an EGT gauge

So thats my preference, in my bus I have oil temp as the water temp gauge, a volt meter for the leisure batteries and an oil pressure gauge thats not connected lol.
Something worth hooking up while adding all your stuff in is a light on the dash thats connected to the fan with maybe an override switch, that way if water temps are high you can see when your fan is running and if your unsure you can flick the switch to check its getting power. I have had it a few times with air locks where it would get hot and I would have to check the fans to find they work fine but its actually low on water and airlocked.
Hope this helps