I actually was in the process of writing up this trail, but for Mt Edwards. I thought my Labor Day jaunt was a worthwhile trek, and was surprised that it wasn't covered in SP. Imagine my chagrin when I found that you just did this today...sigh...
Since I doubt I can be nearly as eloquent as the great job you've already done, you may want to attach this route to Mount Edwards as well.
There are a couple of things that I'm not agreeing with, although admittedly, they are opinions... I would say that from Argentine Pass to Mount Edwards it is just a Class 1 walk-up. Although I didn't go to McClellan due to my late start, if one was to stay on the ridge to it, it didn't look any more difficult. (The ridge between Mount Edwards and Grays Peak is where up to some Class 2+ can be found...) Also, I'm 99% certain that it is half a mile between Mount Edwards to McClellan Mountain, but this can be easily verified...
Regardless, great job! :)
The only reason I called it Class 2 is that it wasn't along an officially established trail the entire way, but you're right that the difficulty is really Class 1. I have added that explanation into the page. Also, I changed the 1/3-mile to 1/2-mile for the distance between Edwards and McClellan; I figure it's better to expect a little more length and maybe get less than the other way around.
As far as the page you had in mind goes, I'd go ahead and do it. I don't think it would be redundant since this page is for a different mountain and people wouldn't look here for Edwards information, though I do see your point about attaching to Edwards.
I was actually starting work on an Edwards route from Argentine Pass myself, but if you'd like to do it yourself, please go ahead. I've done plenty of pages and am by no means trying to hoard an extra one for myself. Plus, you can describe the trail from Horseshoe Basin, and I can't. If you'd like, feel free to include my directions to Argentine Pass from Waldorf and Georgetown as an alternate approach. And I can attach pictures I had planned as route photos, including a diagram of the route from the pass, and let you use them or not use them as you wish.
Just let me know what you plan to do so we're not working on the same page at the same time!
I could also do my planned page as a TR attachment to yours or Edwards to illustrate the alternate approach but avoid the redundancy of very similar route pages.
I'm thinking that the only difference would be the use of the west side of Argentine Pass trail, especially since you pretty much have to go to Mount Edwards to go to McClellan Mountain (preferably anyway...) In essence, I would only be describing Argentine Pass trail.
It would make more sense--in my opinion--to attach this route to both McClellan and Edwards--although it may need some editing--and add a paragraph regarding the start from Horseshoe Basin.
I'm not that concerned about who gets credit, as long as a service is provided to other mountaineers. :) (Especially since this is such a good route.)