I am contemplating buying Attack on Weathertop though I am thrown off by the 2 figures I already own, Frodo and Aragorn. I have already had a duplicate of gimli but it was easy to turn his body into a Rohan soldier(as the torso is covered by Gimlis beard) and his beard and helmet into a different (yellow) dwarf. However, Aragorn's torso and Frodos hair are both very distinct.

How do you reuse your main character's parts? I can imagine this is a big problem with Gandalf and Bilbo and will grow in the next Hobbit wave.

First thing that pops into my head for Aragorn is either another Ranger or perhaps Faramir.

If you like paying attention to such detail, you could always hand Aragorn a grey cape (Gandalf's) and have two versions of him: Strider (perhaps add a black cape to this one),

and Aragorn with a Lothlorien cloak. Frodo already has that as a difference in both variations. I myself don't normally re-use main characters like these, instead, I would make sure to have all

movie variations possible with that outfit, and then just be creative to use remaining stuff for other figures. For instance, duplicate Frodos in Shire apparel could be used for random Hobbits.

And otherwise, see if Aragorn's legs may work for a custom Rohirrim, head/hair for any figure, and torso for a Ranger.

Or just replace the head, add a dark green/brown cape and you've got the basics for a Ranger of Ithilien.

For Bilbo, you could change the hair to a similar piece of a different colour and pretend it is a Hobbit villager.

And otherwise, see if Aragorn's legs may work for a custom Rohirrim, head/hair for any figure, and torso for a Ranger.

Or just replace the head, add a dark green/brown cape and you've got the basics for a Ranger of Ithilien.

Yeah, I was thinking of making him a ranger, but the necklace is unique to Aragorn, I guess I'll have to ignore it.

For Aragorn give him a green cape and the green hood from a Mirkwood Elf and you have a Prancing Pony version. Frodo's torso is actually nicely generic and can be used in a broad range of themes. It would make for a nice modern teacher or professor. The only limitation is the pink at the neck. If you are wanting to reuse it in LotR, then swap around a head legs, cloak and hair and call him Fatty Bolger. The Hobbit who got left behind (and left out of the movie).

I made some Elves using some LOTR and other minifig pieces, some from CMF and castle. Just started a thread if you want to check it out. It's called Elf lords.