There's an awful lot to consider here. Really, there's an endless cycle of extrapolation that could evolve from this one question. But when I think about this choice and the immediate consequences regarding the Ring, it occurs to me that the first question is "How much help could they have been to Frodo and Sam?" It seems clear that stealth was the fellowship's only viable course in approaching Mount Doom. If the Three Hunters are still in the company (and hence, not the Three Hunters at all), stealth becomes more of a problem. We know that hobbits can be inconspicuous when it suits them -- not so men, and most certainly not dwarves. So without even considering the changes this decision wreaks in Isengard, Rohan and Gondor, how does the company go about infiltrating Mordor and reaching the Cracks of Doom?
There is also the question of Smeagol to consider. I would assume that if Aragorn is still calling the shots, Smeagol is dealt with in some fashion and is not there at the end -- or at least not free -- to ultimately rescue the entire enterprise. So what happens when Frodo claims the Ring for himself and the fate of the Third Age is balanced on the razor's edge? The pragmatist in me says that, at this point, somebody is going to have to dispose of it (and, most likely, Frodo himself, in the bargain). It seems a safe bet, given history and what we know of the Ring and men that Aragorn would be unable to do this. It seems to me that Gimli could do it -- he seemed sure enough in Rivendell -- although his willingness to destroy it when he could not and his ability to do so when he actually could might be two different things. Legolas? Who knows? I've had this debate in my own mind over and over again. Would dependable old Sam chuck his master, Ring and all, into the abyss?
There are so many facets to just this one aspect of your question that volumes could be written on this topic alone.
But that would require someone much more knowledgeable and dedicated than poor old Deagol.
