Looking at it I don't think there would be room in the case for that circuit and the batteries needed. The valves extend too far down into the bottom of the case.

A DAB conversion would definitely be the best, but I'm not aware of any DAB kits that you could use. I guess you could remove the guts of the new Pure Evoke-1 set and cram it into the box. Not sure there would be room for that either though.