I definately want to be able to carb/ serve at different pressures. Do you think that there would be any need to have larger manifolds? Like two 6 way manifolds? I was just thinking that way I wouldnt be stuck only putting 4 kegs at a certain pressure. Might be overkill though.
I'm not sure that I would define any of this as a matter of need, lol.
I think the key question is, what do you really plan to do regarding separate pressures? Personally, I would keep it fairly simple to start. You can buy in a way that would allow you to expand without paying much of a penalty. For example,
If you bought 2 4-way manifolds, you could chain them and have one pressure.
If you decided you wanted 2 pressures, you could put a secondary regulator between them.
If you then decided that 2 pressures were fine, but you wanted more than 4 kegs at the same pressure, you could buy another 4-way manifold and chain two of them together.
If you then decided that you really wanted 3 pressures, you could buy another secondary regulator to put between the chained manifolds.
If you get the check valves with flare fittings, you can move your gas lines from one manifold to another and close the check valves where there is no line (that would be the best way to have more gas ports than you can fit kegs, rather than having more gas lines and keg disconnects).
Start somewhere with 1 or 2 pressures, and learn what you will really value.