I've thought of smaller tardises before too, and agree that for most games they'd probably be more practical. As for checkmating difficulty, it seems that Charles was probably relying on the fact that Kings are confined to them, and so presumably the idea (or at least one possible strat) is to get as many offensive forces inside the tardises as possible while the board is still full enough to prevent too much tardis movement (as in the opening setup) and then use that to attack where the king can't escape. And potentially keep the armies spread‐out enough to prevent too much possible movement.
I agree that stopping teleportation whilst in check (after all, The Doctor sticks around until the danger's gone…) looks like a viable option should this indeed be unwinnable in practice
I've thought of smaller tardises before too, and agree that for most games they'd probably be more practical. As for checkmating difficulty, it seems that Charles was probably relying on the fact that Kings are confined to them, and so presumably the idea (or at least one possible strat) is to get as many offensive forces inside the tardises as possible while the board is still full enough to prevent too much tardis movement (as in the opening setup) and then use that to attack where the king can't escape. And potentially keep the armies spread‐out enough to prevent too much possible movement.
I agree that stopping teleportation whilst in check (after all, The Doctor sticks around until the danger's gone…) looks like a viable option should this indeed be unwinnable in practice