Hi there,  to the most degree Robbie already hit the nail on the head
with the reservoir being "the" shock-absorber for short, heavy bursts
of lots of air required, whether that be due to lots of notes playing,
or lots of ranks being on at the same time, or most likely: both!

Most of the other points can all somewhat be rolled into one.
Of course the arrangeurs of yesteryear have long known that this can
occur (or maybe it did not because of the tunes they tried to arrange)
and the solution is quite simple, indeed: do not exceed "x" amount of
notes playing at the same time, with that "x" being a different number,
depending on which make/model it is being arranged for.

Even on a (relatively) modern organ, such as the Raffin 20/31 street
organ, it is possible to arrange music, that will exhaust the organ
beyond its own means.  Again, there are ways to tape notes shut
(exclude from further copies) so that this doesn't happen.

Another point you mentioned does play into this scenario: maintenance.
If an organ falls into slight disrepair, then a tune that _usually_
would "just" play okay will suddenly sound asthmatic.

Albeit some of my repair-customers are unwilling to agree such things
are possible, we often encountered on our large street organ, that
air-issues would arise depending on heat and humidity (mostly the
latter).  We would then counteract this by trying to raise the humidity
in the area, but in the meantime we would "fix" the issue by using
organ books that, quite simply, are less demanding.

Now, a solution to fix the organ for "future" style arrangements, that
simply demand more air, is also quite easy and logical: provide more
air!  This can be achieved with changing the gear ratio between pump and
tracker and thus the overall crank speed.

In the UK "progress" was made and everything (well, not quite everything)
switched to blowers -- if the blower is insufficient, get a better one!

Development certainly has happened, even for the Raffin organs, as the
larger organs all use twin-double bellows to be able to provide ongoing
sufficient air-flow, and -- if all else fails -- you can follow Robbie's
advise and just shutter one of the stops manually.

With my own 20-note musical arrangements, I always inquire for what
type of 20-note organ it is meant for, so that I can either advise
for or against the purchase of one of my arrangements without ending
up disappointed, that it just won't work on said instrument.  Or I
custom-edit, making the arrangement somewhat less "complete/full" but
playable in exchange.

As arrangeur you can really only do so much.  So my advice to Andy Park
would be to restrict himself to what at least 80% of well maintained
organs can play on average; if it then fails he can point to the organ
as not sufficiently maintained.

Musically,
Ingmar Krause
Coquitlam, British Columbia, Canada
http://www.grindorgans.com/ 
http://www.drehorgelmusik.net/