I have been using a Rieger Tip profiler (which I bought from Bob Williams!) for at least 20 years and I love it. I initially used their standard pattern block for a while and customized the profile by using tape to increase the spine area thickness. Eventually I had Rieger make a new pattern block for me with a more radical spine and thinner channels, based on sending them a finished reed to copy.
You asked a question about limiting the distance that the machine cuts which I'm not sure anyone has answered it yet. You can add spacers to limit the travel of the blade carriage (or for that matter remove spacers to allow the machine to cut further into the blade if you want). On my Rieger (I would imagine you could do the same thing on any tip profiler) you would add the spacers on the right side of the rod in front of the leather washers. I use Grolsch type rubber washers (from Grolsch ale), but anything to add space will do. I cut the washers so I can slip them on or off without dismantling the machine. By having 5 or six of these washers you can limit the machine even to only a fine adjustment to the last mm at the tip if you want (or anywhere in between). Additionally you can push the reed slightly beyond the index mark to take slightly more cane from the very tip area since the taper continues slightly past the index line.
The beauty of these machines is that you can have several types of pattern blocks for different reed styles. From my experience on the Rieger, you can swap out the pattern blocks in a few minutes.
Let me know if you want to me send you a photo of what I'm taking about concerning the washers and limiting the blade travel. The Rieger is an amazingly flexible machine which can be customized with different pattern blocks or by modifying the blocks with tape or expanding or limiting the area it treats by adding or subtracting the leather or rubber washers. I have found a really amazing tape to customize the patterns which is made of thin 5/1000" aluminum which is used for taping ductwork together and works wonderfully. You can get it at a good hardware store.
I hope this helps,
Associate Principal Bassoon, Houston Symphony