After extensive conversation with K, we settled on a parts list. Here it is:

And we created an assembly plan:

Steps in assembly (electrical and electronic):

1) create the power bus. Basically this is pair of 16awg wires that wrap around the back of the coat at hip length. Tails are spliced in to connect to the power connectors for the regulators (8 F mini-tamiyas), to the battery (1 M mini-tamiya), and to the arduino (1 M power jack). This is mostly working with the wire: cutting to length, stripping, attaching pieces with a heat shrink crimped butt connector (the two ends from the bus + the tail). 10 pairs of joins per coat.

1b) The F mini-tamiya plugs go on each tail that will connect to a regulator. If the related strand ends really close to the power bus, the leads from the plug go straight into the splice on the bus; otherwise, a 16awg wire runs from the power bus to where the strand begins (and where the regulator will live). [footnote 1] (lineman’s join, solder + heatshrink)
1c) One M mini-tamiya goes on the tail that goes to the battery; (lineman’s join, solder + heatshrink 3pr)
1d) one power jack goes on the tail that goes to the Arduino (screw terminal block + electrical tape)

[footnote 1: Note for measurement: as you’re figuring out where each strand starts relative to the power bus, keep in mind that you have 20-24″ of additional run. This comes from the connections that result from the tails on the mini-tamiyas, the regulator itself, and the tails on the connectors between the regulator and the strand. Detail: the mini-tamiya has a 6″ tail; with 2″ lost on each end, that’s at least 8″ added to the run between bus and regulator. The regulator itself has 7cm leads on one end, is about 5cm, then has a 15cm lead on the other end. To the regulator output, we’ll solder a power connector, and a power connector to the leads from the strand, adding 2×6″. We can trim all these substantially if the strand starts closer to the bus]

2) attach a F mini-tamiya to each set of battery leads (lineman’s join, solder + heatshrink 3pr). Note that this lead has to connect to the lead (1c) from the power bus.

3) add M mini-tamiya to each regulator input (lineman’s join, solder + heatshrink 24pr)

4) add 22awg F to each regulator output (lineman’s join, solder + heatshrink 24pr)

5) add 22awg M to each strand power (lineman’s join, solder + heatshrink 24pr)

3) create 22awg inter-strand connectors, length depending on layout (22awgx3, inter-cable connectors on each end, lineman’s join, solder + heatshrink 21triples). Some strands may connect to each other directly and therefore not need an inter-strand connecting cable. We need to know how many inter-strand cables we need, and how long.

3a) create a connector from the first strand to the arduino. (lineman’s join, solder + heatshrink 3triples). how long?

4) assemble protoshields; solder inter-cable connector to SPI pins; solder inter-cable connector to pins for touch sensor. Add potentiometer and program select switches.

5) plug it all together, and debug.