Welcome @Commodorewolf to the Maslow forums! I’m glad you’ve found your way here 
This is limited more by your choice of router than the machine. We have cut with as small as an 1/8" diameter bit (that I know of), but a 1/16" bit with an adapter collet or a larger shank should work as well. As a side note, the machine doesn’t perform well with large diameter bits. The maximum feed rate is currently 1,000mm/min (~40ipm), and to get the correct chiploads you would need a low rpm router.
In the (old) stock design, the fence would get in your way when you get too close. Solutions to the problem are either to use a similar thickness strip for a fence, or to do away with the fence. I like the former myself. While I have yet to implement this on my machine, I plan on having 1/4", 3/8", 1/2", 5/8", and 3/4" strips on hand for that reason.
Similar to the fence question. At the bottom of the machine, the fence will support the sled. I do this all the time with my machine with no problems. Again, sizing the fence to the material is important. At the top, no support is needed since the CoG is low enough. The sides may need “skirts”, which really are just like the fence I keep referring to. See @Bee’s thread, 80 Dollar, 60 minute Frame Build aka 80/60, for more details.
In theory, you could make it so the start and stop of your cuts are at the top, so that the part falls away as it finishes it’s cut. However, the easier and more common solution is to use tabs. Many CNC’s without vacuum tables will do this as well to keep parts from flying off the machine as it’s cutting. I keep a sharp 3/4" chisel on hand so I can cut the tabs after the machine is done. It’s quick and easy to clean-up.
Three things to look out for in your router selection:
- Variable speed range.
- Ease of mounting the Z-Axis kit.
- Size of the router and base
Issue 1: The Rigid R2200 router (the recommended stock one) has an RPM range of 10,000-20,000. I checked the Amazon listing you have linked and didn’t see RPM as one of the listed specs. I would strongly recommend making sure you can go at least as low as 10,000, if not more. The reason for this has to do with the above mentioned feed rate and the ideal chipload for a bit. See my thread, Increasing the Max Feedrate?, for more details about the relationship of speed and chipload.
Issue 2: This may be harder to figure out from just the Amazon listing. With the Rigid router, the Z-Axis motor connects to the base’s depth adjustment leadscrew via a shaft coupler:
From what I can see, it looks like you can remove the depth adjustment knob and attach the Z-Axis motor to that, much in the same way that you can with the Rigid router. I’m not sure, however, if the Z-Axis motor and the router itself might collide at some point in it’s range of motion.
The other thing to keep in mind with the Z-Axis is that, at least with the Rigid router, there is a fair amount of slop in the depth adjustment mechanism. We’ve solved that issue by preloading the router towards the material with a bungee.
Issue 3: I don’t think this will be an issue from what I can see with the Milwaukee. Some routers are really bulky (especially those that are available in the EU) and have been tricky to get to work with the triangular kinematics kits. Those kits would be either linkages, in the case of the top mount or 45 degree kits, or bar’s awesome ring kit. There are additional derivatives of these designs as well, but those are the major 3.
For more info on the triangular kits, here is some pretty heavy reading:
Very long development thread for Triangular kinematics: Throwing my hat in the sled modification ring
Link for @pillageTHENburn’s 45 degree kit: Linkage kits are now available! 🎉
Link for @dlang’s top mount kit: Metal Top Pantograph kit available
Link for @bar’s ring: Newsletter Ring Development
Accuracy tests for the different kits: Triangular Linkage Evaluation Criteria and Measurements
If you have any other questions, let us know! Remember, there are no dumb questions!