The above is actually my second keezer; the first used an old freezer that finally gave up the ghost, bought a new one.
In my original keezer I had 3 taps, then added a 4th, then later a 5th. So there's room for expansion. When you lay out the spacing on the faucets (3", btw, between centers on mine), mark out the additional ones. Put a tiny dimple in the wood with an awl, small enough that you can't see it unless you go looking. Far easier to get them to line up correctly and spaced out properly in the beginning. Then when it comes time to add a faucet, you only have to find that dimple and go from there.
When the time comes to look for a keezer, take along some paper plates or similar cut to the diameter of your kegs; that way you can lay them on the floor of the display model and see how many you can get in there.
One other consideration: virtually all chest freezers have a compressor hump. It's not possible to get a keg or two on top of that unless A) you make the collar very high, or B) get some pinlock-form-factor kegs. Morebeer sells torpedo kegs, one style is shorter and wider, one style taller and skinnier. The tall/skinny one is essentially the same size as a standard ball-lock keg.
I can get the shorter/squattier torpedo kegs on my compressor hump, but not the taller standard size, given my 2x6 collar dimensions. You can of course go to a taller collar but the higher it goes, the more difficulty in getting the kegs in there.
BTW, check my signature below for an easy way to build a keezer that allows it to be easily moved, and requires no glue to assemble.