Well with Marin being confirmed for the Link's Awakening Pack, there's only 3 more characters to guess, and there are plenty of possibilities.
For the Phantom Hourglass & Spirit Tracks Pack, as much as I would love Byrne/Staven to be a playable character with his mechanical arm being his weapon, I'm guessing the new charactrer would have to be a noticeable one that made an appearance in both games to link the pack together, So it could either be Linebeck or the iconic Phantom seen in Phantom Hourglass's multiplayer and Spirit Tracks's story.
Linebeck's weapon could be the grappling Hook with a water element. With the Phantom (possibly possessed by Zelda), The weapon could be the Sword and Shield they use with a Dark Element that lets them use the abilities seen in Spirit Tracks e.g Teleporting, turning into a bolder to run over enemies etc.
For the A Link Between Worlds Pack, I think because two characters are in this pack, Yuga is almost guaranteed to be a character with his magical wand having either a lightning or Dark Element (likely Dark).
As for the second character, I'd like to say Ravio with his weapon being his bag which contains and allows him to use the Tornado Rod, Sand Rod, Fire Rod and Ice Rod as part of his strong attacks. Hilda is also a possibility as she has her staff to use as a weapon.
Those are my takes on the 3 unconfirmed characters. There are other characters Koei could choose from, but I believe the above I mentioned have a high possibility of making it into Hyrule Warriors.
It would be weird to have two of the same exact weapon, even if it's for different characters. So even if the chain chomp were going to be for Linkle, it still wouldn't make sense since Link has the chain chomp. You can't have two of the same exact weapon. It just wouldn't make any sense.
I should point out that Dynasty Warriors has done this before, even to the point that some character's movesets were very similar to each other. This was very common in Dynasty Warriors 7 with a majority of the playable characters.
But even if Linkle has the BowWow, It could still have a unique moveset as the BowWow is actually part of the moveset. It wouldn't count as being the same as Link's Gauntlets because the Ball and Chain in Twilight Princess is the default weapon and the BowWow in the Lv 3 gauntlets is purely a cosmetic change which isn't used any differently to the other tier weapons.