So what would all the primary means be? I they were to make weeklies the primary means, what others would be set up as primaries? Do remember that not everything can be a primary mean.
Also, if the weeklies are just one primary method among others, then the 16k you can get from weeklies would be roughly equivalent to what you could get from other methods. However, the weeklies AFAIK are currently not the, or a, primary method for merits; so the current merit value for weeklies would likely change if they became the, or a, primary method.
What the primary means are isn't for me to say but, as FDev have indicated, most things should be roughly equivalent. No doubt that should skew according to power, LYR gaining more from exploration than ADelaine, for instance. That may already be accounted for by multipliers though.
So, maybe it is all of them? I'm not sure why they can't all be primary means.
And yes, the weeklies, if they were another primary means, would earn as much as the other methods but when you've done 5 they run out. You can either wait till next week doing other stuff (or not) or you can explore the rest of the PP activities the same as people who don't use the weeklies.
5 weeklies being roughly equal to 5 fairly well done other activities sounds fine to me. I'd probably give them a little boost so they stay relevant and tempt people who otherwise wouldn't do any and don't want to figure the methods out but not everyone would agree.
The limit of 5 a week largely mitigates any unbalance you might find from weeklies being too generous.
It's kind of a pointless comparison though as the weeklies are finite missions where player led PP activities, say, bounty hunting end when you've had enough.
I think it's good that they 'pay' well though.