When a government employee retires after 30 years of service and has an annuity worth, say, $1 million to be paid to them for the rest of their lives as a retirement pension, the government doesn't come away and take 40% of the annuity in one year at the top bracket, right? But that's what it does with an entrepreneur who might sell their apartment building.
The thing to do is to create a reserve and have an income averaging opportunity with the capital gains. It's not rocket science. It would be a very practical way to cushion that capital gain.