It has one fatal flaw...
It makes too much sense! No wonder NASA didn't go for it.
The crew carrying version is interesting. Was it meant to be a lifeboat or was it intended to be a two-way vehicle? One of those could carry emergency repair equipment to a Shuttle in distress. A couple of those could bring down the crew.
"Of all the words known to men, the saddest are 'if only when'".
- Unknown