Salut, tout le monde,
Thank you for all the input. I was not expecting this many replies :3
To answer some questions, I want the machine to be accurate down to 1mm or less if possible. The machine will scan a paper that is 24" wide and vary in length up to 5' (comes off a roll). The machine will only be able to work up to 5' paper length and nothing more.
I need the machine to scan the side of the paper looking for a set of marks that were made by our printers. One mark tells the machine where the start of the paper (work area) is, then scan up to a determined length looking for another mark to tell it where it ends. The images will be printed in rows going from one side of the paper to the other in a fixed matrix so that the machine will simply need to cut the area where an image is supposed to be, regardless of whether there is an image printed or not. All images will be of the same shape and size.
Additionally, each row will have a start and end mark (essentially the same mark used to determine the start of the work area/paper will also be used as the start of the first row). The machine will have to look for the end mark, then scan a predetermined distance looking for another mark in order for it to know if another row of items is present. If none are found, the machine simply counts one row then returns to work on that row which was detected and cut it. Once it's all done, it returns itself to the zero position. These marks will be used for the machine to align itself with the paper.
I hope this is making any sense. I am trying my best to describe it. If not, I happen to be an artist and I would be willing to illustrate it in order to show you what it is I am trying to describe.
For now, I'd like to build a small prototype that simply cuts one or two shapes where I tell it to using marks on a small sheet of paper, possibly size A4 letter. I also plan to use centimeters as the preferred unit of measurement for the matrix on the paper. However, I need it to be precise to 1mm, as I need it to cut inside of the image to about 1mm or 2mm (I'll decide on which after). This will get rid of any possible stroke lines that the original image may possess that are unwanted.
Our printing program (Wasatch) allows us to print images in a matrix that also uses the cm. So, we could place the images in predetermined areas. The image will always be printed in that very same spot each time.
I believe this is possible and should not prove to be too difficult to make, even if I am not too familiar with Arduino. It'll be a learning experience for sure, which is where the fun of this project lies

Questions;
1. What type of scanner could I use? I hear Pixy could work. Would a Pixy camera be overkilled when I could get away with a cheaper and more reliable IR scanner of sorts?
2. Where could I purchase parts such as chrome plated rail bars that are 5' in length? (I am willing to make the machine shorter, perhaps to about 4' but no less wide than 24".)
3. Can all this be accomplished?
Any questions, please ask. I will answer any questions to try and explain what it is I'm planning on building. It is essentially an X, Y plotter but with a few extra bells and whistles, and a very sharp blade :3 Thank you all very much and I hope I managed to give you guys a better idea.
Merci beaucoup,
~Sat