If you look at printers that have more than one extruder (Hyrel, printrbot metal plus, ...), they are usually spaced horizontally. Say you have 4, all separated by 5 cm (2 inches), then if the left hot end wants to print on the right border of the printbed, that means the 4th hot end is 15cm (6 inches) out of the printbed to the right. Which means that your total travel must be : printbed width + 2 times 15cm !

To avoid this issue, ORD solutions had an idea, they spaced their 5 hot ends on X and Y as a square. That means you loose less travel on one axis, but you loose on 2 axis instead. A kind of trade-off.

See their explanation here : https://www.kickstarter.com/projects...d/posts/920926

See what I mean ?

That is why people are try to develop hotends that take in multiple filaments : that actually solves a few issues (levelling a printbed with several hotends is more difficult).
To see what I mean look at this : https://www.kickstarter.com/projects...ti-color-3d-pr
The issue of that however is that all filaments go through the same hot end, meaning you need filaments that all need the same temps. Which is not the case if you are looking for support material usually.