There's no such thing as "own blocks". There's a single world-wide winner of the mining competition per 10 minutes. So if you want to have free transactions 50

There's no such thing as "own blocks". There's a single world-wide winner of the mining competition per 10 minutes. So if you want to have free transactions 50% of the time, the way to get there is to take the current world-wide mining capacity, and replicate it. That's obviously not a viable tactic.