More importantly, has anyone done this and still have their compete complement of fingers left?
Are you expecting anyone to be able to type a response?
It wouldn't be any more dangerous than a regular bench saw if you included the features that a bench saw has - which is a guard for the blade (which shouldn't be too difficult to achieve) and a means to stop it quickly. You can get in-line no volt release switches which you could screw to your bench in an appropriate position. But the circuitry of the saw is part of that two. A bench saw (if its been manufactured in the last decade or so) should actively stop the blade in a few seconds, rather just turn off the power and leave the blade spinning. Your circular saw might do that too - but it uses power to do that, so releasing the trigger will stop the blade, but pulling the plug (or using an in-line switch) might just leave the blade spinning.
You also want to create a reliable fence and maybe a mitre guide.That and making sure the saw is attached firmly enough and straight enough.... means you've sort of gained a bench saw and lost your circular saw - getting it set up and working well enough to be be properly useful rather than a quick bodge would mean you wouldn't want to un-set it very often.
The other question is - are you going to use it for? Since I bought a rail saw I've almost never switched my bench saw on - I only use it for cutting repeated batches of material. For everything else the rail saw is quicker, easier and more accurate. Its also more space and effort efficient. If you want to cut an 8ft sheet you only need yourself and 8ft of clear space - with a bench saw you need 8 feet in front of the blade, 8 feet behind the blade and two people to handle the board.
You can make your own rail saw in about 5 minutes.