Pictures of major mechanical modifications:

Addition of real power switch.  The spring contacts at the bottom of the battery compartment were separated (cut) and slightly shortened; then the wiring to the switch was soldered to the spring contacts. Note, a good roughing with fine abrasive paper and the use of a quality flux will greatly assist with soldering.

Note that holes were drilled in the plastic ribs to easily route the wires.  After soldering to the push-locking switch, use an Ohm meter to verify you have correctly wired the switch.  Hot-melt glue can secure the switch and is preferable to "super glue" which can wick into the switch and damage it.

I used a Dremel tool to drill a small hole directly where the elastic-power (soft switch) was located.  The LED can be secured with UV adheasive, hot-melt glue, or quick-set 2-part epoxy.  A 1K Ohm resistor was used for current limiting; select based upon LED color.

The LED and resistor are wired directly to the upper battery spring contacts on the circuit board.

On the case face plate, I used a drop of UV clear acrylic to form a lens and to plug the hole where the original rubber plunger was located.

For this mod, I wanted to extend the programming to rolled-pins mounted under the battery cover.  This is not particularly difficult, but is somewhat tedious.  The pins were removed from a quality DIP IC socket and held in place using Kapton tape across the back battery compartment.  The pins are positioned with forceps from the back and carefully pressed against the tape to secure a liquid seal.  Then a few drops of UV adheasive will set the pins until the hot-melt glue permanently secures the assembly.

Just the soldering of the jumpers to the system board and case reassembly remains.

Satisfaction for a completed mod.