Who I Believe "Hinted" Each Skylanders Gimmick:
Giants -

Stump Smash. His large size in Spyro's Adventure may have influenced Skylanders producers to do a game based around giant Skylanders.
Swap Force -

Eye Brawl. The way the "top half" (Eye) had an attack and how the "bottom half" (Brawl) had two attacks, the fact that they were separated, and the way they each had a role could have very well brought up the idea for swapping Skylanders.
Trap Team -

Trap Shadow. The way he had a special weapon (that was also shiny) that signified his top half and captured enemies in his bear trap may have brought up the idea for trapping villains and "Traptanium" weapons. I kind of doubt this one, though.
SuperChargers -

Tread Head. I mean, he is a Skylander that can drive a vehicle for combat. I can't argue with this one. He may have slightly influenced Skylanders who can drive vehicles. I thought a game centered around vehicles was bound to happen anyway, though.
Imaginators - Modding vehicles. If anything from SuperChargers influenced the idea of making your own Skylanders, it was definitely the fact that you can adjust vehicles' appearances and powers in SuperChargers. Although, Senseis and Villains were mostly likely influenced by Trap Team.