T3S is rebuildable like the PT heads. The T3SD is dual coil, and while some have said they rebuild them, others have not succeeded. Although they might be rebuildable to single coil form. No idea about the e-smart. (The T3S coil has a smaller diameter "washer" part of the head than the PT heads. It will usually work fine in the PT style. The PT style won't work in the the T3S.)
For the small form factor, you might also consider the PT Mini or the Davide mini. Both can use PT heads as well. Since you already have the PT, it might make sense to only need to stock one kind of head.