Thank you for the question, Mr. Sorbara.
What you are proposing, that is to say not taxing income, is one way of doing things. The same tax rate would apply, and there would only be additional tax, which would not be returned, when the money is taken out of the corporation. That is when you see tax rates of 72% or 73%. That is one way of doing it.
Here's another way: let's say the low income tax rate would only apply if you reinvested those funds, otherwise you would be subject to the general tax rate. All of this complicates the Income Tax Act, because it is more difficult for SMEs to comply. There is always a cost to pay. You have to chose between simplicity and fairness.
You could also set a threshold. If you want to target the richer group, you could set the first tranche at $500,000 of invested capital in passive income, and it would not be affected by the rules. The $500,000 is equivalent to the maximum amount of business generated that allows a corporation to benefit from the lower tax rate. That figure could be a guide.