This would be nice to have, since right now combos are an all-or-nothing deal. Granted, they arn't nearly as hard to put together as tiles, but with the complex combo cycling being put together it can take some time.
Combo Grabbing
On the contrary, I think they are harder than tiles. You have to set the walkability, any offsets, the combo type, any combo annimations, as well as the tile itself. It's a hassle. Your suggestion is a good one that I think should seriously be considered.