Jazz I understand what you are saying but from the little I have seen during researching building a machine Profile rails are very expensive & this would be more likely to put me off trying to be honest. If you are lucky enough to have money then I suppose you may not think of them as being expensive but on the limited amount of money I have available it's just not really possible & at my age I would probably be dead before I could save up enough lol.
If I do manage to build a machine I'm not actually sure just how much use it would get or what sort of accuracy I would require. Yes I can think of one or two things I would like to do with it & I realise that once it is done I might be able to come up with other ways to use it but I still can't see it ever getting more than a few hours a month run time.