I looked at the book and made some counting for the lines different characters have... and am suggesting a new idea.
Let's take first an excerpt that begins from where I suggested (p.298) and read it through to page 305, ending with Gandalf's line "But we must not use the wood - not unless it is a choice between fire and death".
There the story changes quite remarkably as then the getting forwards gets actually tough and the snow starts to fall etc...
And taking a few pages more we'd get everyone speaking at least a few lines.
My count of lines for every character from the end of 298 to the halfway of 305 is as follows:
(short = 1 to 2 rows, medium = from about 3 to 10 rows, long = more than that)
Gandalf - 10 med. + 5 short
Aragorn - 4 med. + 5 short
Gimli - 1 long + 1 short
Legolas - 1 medium
Boromir - 1 medium
Frodo - 2 short
Sam - 1 med. + 2 short
Pip - 4 short
Merry - 2 short
The narrator - about 2½ pages
So unfortunately those roles we're most unsure of are the ones that have the most to do...
So a Gandalf and an Aragorn?
Any ideas?