Fair enough on the blanket part, I went back and looked at Nixon, and it is basically a blanket within a five year period. I guess that has enough precedent.

But the only reason that constitutional scholars don't agree yet about secret pardons being retroactively handed out like "get out of jail free" cards, it's because they didn't think anyone would be audacious enough to do it.

I just don't see how Trump's pardon power can be allowed to remain after he's no longer president, and to use his power this way, to shield his cronies from exposure of their crime until they actually have to admit guilt once already caught (and this is only if he has a secret one for himself too. He would never pardon others to make himself look more guilty than he already does).

It's obstruction of justice, and not at all in the spirit of checks and balances. In fact, it enables the worst parts of having a king that they wanted to get away from, lawlessness and absolute power. This is precisely why it would be struck down.