Well here's one for you.!! . . . . How about building vertical machine and save a load of space.? (Almost go thru Garage Side door then.!!). . Think Panel saw like you see at BQ etc.

My machines been working in a vertical position now for over a year and it works perfect and that's cutting aluminium. It's also in the worst vertical position because it's having to lift the whole gantry vertical not horizontal. (It's actually back on it's feet at the moment but that's for repair reasons.!!)

If I was building a 8x4 router just for wood then it would definitely be built vertical even if I had the room has it's so much easier to keep the workshop clean let alone the space saving and other benefits.
90% of the chips fall with gravity so land at the base of machine, this natural falling also helps increase cutter life and give better work finish has it's not re-cutting chips.
Because it's vertical it's very easy and simple to build an enclose around it using cheap 2XG doors and contain all the mess inside. (Think Large wardrobe with see thru doors.!)
Work handling and access to parts on bed is so much easier has now your stood directly in front to fasten or remove and not bent over struggling to reach.

Like I say plenty of positives and No real negatives.

Now what do you plan to use for Linear motion.? Ie: R&P or Ballscrews has this will play a part in how you design the machine.?