From what I have heard and learned about band organs is that they are
voiced on "high pressure", and are designed to be portable.  I don't see
why one couldn't use theatre organ pipes, as they are voiced on high
pressure (generally about 10" and up (the "Wonder Mortons" are all on
20" or 25" as I remember)).

The main difference is -- and this is an important one -- is that most
of the pipe work in a theatre organ is made of metal, and most Band
Organ ranks are wood.  The disadvantage, if you're going to be moving it
around, is that the metal pipes are "weaker" and would be damaged more
easily.  A disadvantage to both types of pipe work is, if this is suppose
to be in your living room, both type of pipes are extremely loud and
rather harsh when your right next to them (10 - 20 feet).  Another
difference is, that the "strings" on a band organ seem to be larger
scale, more like a gamba or a church organ salicional, than a theatre
organs violins or viole d'orchestra.

I think that for the most part just about any type of pipe work would
be okay, but the big difference is that the sounds that are produced
(when played on the correct pressure for the pipe) would differ, i.e.,
a band organ with theatre organ pipes would sound like a theatre organ
without tremulant).

I have wanted to put a band organ roll box on the pipe organ in the
house where I live, and have asked which is the most common scale, but
for the most part, the response I received was "why would you want
to?".  Well, I like the way that band organ arrangements sound and the
pipe organ we have has over 800 pipes, one could have all the different
common Wurlitzer scales represented as they don't have "complete" ranks
(you would have to add switching to control the pipes needed), but I
could hear band organ STYLE music at a listenable volume in my house.
But I digress.

To sum it up, I don't see why you couldn't use theatre organ pipe work
as long as you realize that the instrument won't be as portable as one
built in the traditional manner, and that it would sound a little
different (perhaps more refined in some ways, although those European
organs are really something).  It just wouldn't be an instrument that a
"purist" would listen to.

My two cents worth.

Ed Copeland
http://www2.bitstream.net/~edcplnd

P.S.:  Century Pipe Organs is only a couple of miles from me, and they
have a warehouse full of theatre organ parts.