I suppose it might be possible to graft on an eggplant or some black nightshade as well, since they're in the same family. Plums apricots and peaches can be grafted and you get space savings, longer harvest season and novelty in a
perennial. Seems like a lot of bother for an annual plant that's essentially a novelty.
Imagine the possibilities with members of the cabbage family grafted onto a Brussels sprout stem.