One compromize to preserve as much orginality as possible, regarding to
those dangerous open mercury switchs would be to replace them with
closed mercury switches.  (It is very strange that someone even THOUGHT
of making the mercury switches open. What if someone turned the device
upside down...?) One common type of switch is a U-tube made by glass,
filled with mercury. Depending on the turning of the tube, the mercury
make a short between the contacts or not.  I don't know the different
types of open and closed switches, but understand that some
replacements should be possible.

OK, one must have to do some modifications to get this to fit, but
still some of the originality is preserved by using the technology from
old times. I think there would be many other situations where
acceptable compromizes between originality, operationality and safety,
can be made by choosing solutions based on old times technology.

That time as nowadays, some solutions may turn out to be better, or to
be worser, and I can't see that anything harmful is done to the
originality of old times technology, if we make desicions that may very
well could have been done that time.

Sincerely Thomas Henden, Norway (Apology for bad grammar. :-)  )