Rickon Stark comes from a prestigious family, yet his role is so small that does he warrant a figure? Bran? Well, it would make sense if he came with Hodor.
Rickon is one character that's questionable at best for the Funko line. I could really only see Funko making a Rickon figure if and ONLY IF Rickon comes back into the fold later in the series. Most likely being played by an older actor.
And I agree on Bran. If Funko does something similar to what Dark Horse did, and offers Bran with Hodor, then I could see that offering working.
Then there are so many other characters to consider. Does Gendry merit a figure? What about Pycelle? Would Varys make for an interesting action figure? These are characters that are really important in the scope of the series. But do they translate for the purposes of an action figure line?
As for characters that I DO think make sense? Others include Ser Barristan Selmy, Bronn, and Lord Commander Mormont.