Modification of a Seiko UC-2000 digital watch

In 1983, Seiko released the UC-2000 digital wristwatch.
It features a 40 character 5x7 dot alphanumeric LC display
(4 lines with 10 chars), 4 buttons and an inductive
transmission circuitry that allows the communication
with a small keyboard (UC-2100), a BASIC computer (UC-2200)
and an Apple-II computer (UC-2301 Interface).
For it's time, it was a technologically advanced and
very sophisticated (and therefore expensive) design.
Compared to normal watches, where all the electronics is
integrated in one chip, the UC-2000 has 6 chips (5 CMOS
and 1 bipolar), 3 of them for the display alone.
I recently became aware of this watch and was able to get
one, and I realized that the UC-2000 may be the way to
make an old dream of mine come true - building my own watch.
Since I am an electronics engineer, I was not interested
in one of those expensive mechanical marvels, I wanted my own
digital watch. But you cannot go into a shop, buy standard
parts and build yourself a wristwatch.
Then I found the UC-2000.
I dissected one (see here), and I think it is possible to
replace the computer core while keeping case, display,
beeper, battery holder and all the rest.

My goal is to build a watch that does what I programmed
it to do when I push the buttons, and that is as accurate
as can be achieved with modern microcontroller technology.

I plan to replace the 32kHz 4bit CPU with 7.5K ROM and
2K RAM with a modern ultra low power microcontroller,
the MSP430F149 (16bit CPU, 60K FLASH, 2K RAM) made by TI.
This controller can run on a 32kHz watch quartz, has internal
voltage and temperature sensors and very sophisticated
clock and power management systems. I will try to implement
software compensation algorithms for temperature and
voltage drift to improve accuracy.

First step: Find out how it works.
One watch has become my object of study and experimentation:
a DATA-2000 that was kindly donated to me by Foggy from the SCF.
A colleague, our company's specialist for tricky soldering jobs,
completely 'wired' the watch (see here) for me (Thanks Ulli!).
I then hooked it up to a logic analyzer (see here).
After finding out where the display, the buttons etc. are
connected, and how the communication works, Ulli worked his
magic again, he removed the core module (see here and here).
The empty 'mainboard' looks like this.

Here is what I found out so far:

computer core module pinout

LCDisplay communication protocol

inductive communication protocol

I connected the 'brainless' watch to the microcontroller
development system (see here), and I mananged (after a few
days of experimentation) to talk to the display (see here).

Next steps:
  write the software

Final steps:
  make a replacement core module with the microcontroller,
  put it in the watch
  ...and hope that it will work as intended