You're describing here a design rule able to emulate an heritage, which is mostly a matter of methodology/dba experience.
With a (real) OODBMS, this kind of *trickery* relational modelisation is not required.
Well and good to use an OODBMS if one is within your options. I make no assertions about whether an RDBMS or OODBMS is more appropriate.
However I will not allow it to be said RDBMS do not support ISA relationships, when they are clearly supported and the relationship follows directly from normalization. It is not trickery, nor even unusual.
Update: Removed inflammatory language that was not meant to be so.
You said you wanted to be around when I made a mistake; well, this could be it, sweetheart.