Is it bigger than changing the size of the goal (the author's preferred solution?)

Yes, I think altering the number of players on the ice is way more radical than changing the size of the goal by a few %... I wouldn't think they are even comparable!

What do you think?

I don't watch enough hockey to know, and never played. But if the goalie can cover 90% of the small goal, and 70% of a goal just a few percent bigger, it makes sense to me that could be a bigger change than changing the number of players.

For a lot of people, it's more than a sport. It's a huge chunk of Canada's identity for well over a century. Changing the number of players on the ice would be like... well, I can't think of an analogy. But they'd never go for that. (Watch them prove me wrong...)

    But if the goalie can cover 90% of the small 
    goal, and 70% of a goal just a few percent 
    bigger, it makes sense to me that could be a 
    bigger change than changing the number of players.

I don't think they're trying to make the biggest change possible, right? I don't think anybody's talking about changing the fundamental nature of the sport. 4 vs. 4 would change everything right down to roster construction, who you want to draft, and other aspects. Also there's now less ice time to go around. etc.

It's also a very coarse adjustment. Versus changing net dimensions, something they could experiment with in small increments at the minor league level.