In my opinion the ratio of inputs to outputs is not significant except perhaps in extreme cases. This can be demonstrated mathematically. Once you have even a small number of inputs and outputs the potential number of connections quickly runs into a very, very, high number.
If you have only one output (A) and two inputs (X, Y) you have three possible patches:
A-X, A-Y, and A-X and Y.
If we have two outputs (A,B) and two inputs (X, Y), we have eight possible patches:
A-X only, A-Y only, A-X and Y, B-X, B-Y, B-X and Y, A-X and B-Y, A-Y and B-X
With two outputs and three inputs I can come up with at least 26 different patches. See how fast the number is growing? Let's say we have a small system with 20 inputs and 10 outputs. There are 200 ways to place the first patch cable. Once we place that first cable we now have 199 possible options for a second cable...and so on. That setup has so many patch possibilities I can't even type out the number. It's roughly 8 with 374 zeroes after it. Even such a small system with a heavy imbalance has a mind-bogglingly huge patch potential. Your numbers are 90 inputs and 60 outputs, roughly speaking? You have 5400 options for that first patch cable, and my scientific calculator gives me an overflow error trying to compute the total number of possibilities. You aren't "missing out" if the number of ins and outs don't match. It's not important in the slightest.
My personal advice is to not worry about trying to balance out the number of ins/outs and instead to ask yourself what you think the weakest part of your system is and address that. What's the one module that would add the most utility to your system?