I have seen a version of the wooden block where someone cut a double width grove in one side, but without that, i feel that working with a 3 blade set would be awkward?..
You'd swap them around so that that they were all getting about the same treatment. A bit tedious, but possible.
It's only a standby - eventually you'd have to take them off to be machined.
I dont really understand why the veritas unit isnt longer - it seems that a great number of machines are greater than 8" width.
It'd still be usable, but I wouldn't bother - the DIY two blade options above are far more efficient.