Reading through recent messages about keyboard layout, I do hope everyone
knows that electronic keyboards (as opposed to those on manual
typewriters) have almost no restrictions on physical layout or key count.
The PCD Maltron keyboard, for instance, places individual keys in "bowls",
one for each hand. Your fingers dip down into the bowls to type. IIrc, the
Kinesis is similar.
I read of triple shifts for Khmer; some mechanical typewriters in the
earlier part of the 20th C. had three shifts.
More specifically, there's no real technical restriction on the number of
rows in the main letter area; there could be one or two more. The real
difficulty is the cost of manufacture in small quantities, as well as a
likely need for custom electronics and a custom software interface.
Maltron probably sells maybe a few thousand a year, if that many. The
standard computer keyboard is made in such huge quantities that people
like me who acquire workable-to-good used keyboards consider their
monetary value to be maybe $2. to $5 US.
The one I'm typing on is a limited-production custom variation of an
"also-ran", specifically an Adesso Eagle Touch. Other than custom keytops
(unfortunately, somewhat amateurish in places), the only difference from a
stock "qwerty" is some minor circuit changes (if any!) to make the extreme
far right key select either Dvorak or qwerty layouts. The rightmost LED
now indicates which layout is in use. The "chip" inside is definitely
custom; that's where the major difference (and cost) lies.
There are "chips" that can be programmed by semi-technical customers to
contain and sometimes manipulate a very wide variety of data; for small
lots, they would be the way to go.
Gateway sold a programmable keyboard; I don't know a lot about it.
This switchable-layout scheme should be useful for keyboards intended for
two very different scripts. It's really unlikely that two sensible letter
layouts would work with the "chip" in this keyboard, but for a significant
fee, one could have any mappings one wants. There's no need to have only
two, but, Good Heavens...
=
For trying out different layouts, some old IBM keyboards (relatively
costly) had removable, snappable key caps; the inner key tops were
unmarked, but almost the size of ordinary keys. I did a Dvorak conversion
on mine just by moving key caps around. The keyboard weighed maybe 2 kg;
it was quite heavy. Unfortunately, the key mechanisms had no cushioning to
limit down-travel; unless you had a light touch, after a while it was like
repeatedly banging your fingertips on a stout table top (or a brick!).
Google (or Yahoo) on [Hooleon] to learn about their products for
non-standard kep tops. They are well made.