I like these approaches because they provide a single and very sharp transition between Theano and LogPy.  The multiple inheritance stuff scares me a bit.  It implies that any time someone wants to use LogPy they'll have to do this.  I also anticipate it'll cause headaches down the road.  I've used both of the systems I've mentioned in SymPy with good success.  I eventually moved from patternify to something like the context manager but patternify was fine too.