While an interesting prospect, it's unlikely we would launch anything like this soon for a few reasons.
The first is that we actually actively encourage people to pick up local SIMs rather than roam internationally. Anything resembling a typical Ting bill would be wildly expensive for international roaming, and a local SIM has fewer issues with data connectivity.
But on top of that, the current rates per MB have almost no margin built in. That is, we don't profit from international roaming at all. Any markup is lost to crediting back or supporting the system that is in place. We offer it strictly as a convenience.
To be blunt, offering a data roaming package at a discount is, at our current wholesale international roaming rates, a great way to lose a lot of money very quickly. As we're not in the business to lose money even with a loss-leader like international data, until and unless the rates we're charged drop significantly, I don't see this changing.
Our international roaming rates are set largely by our providers, and while we're working on getting those prices down, in the interim it's still faster and cheaper for all involved to encourage local SIMs.