"I don't follow how putting electrical tape around the ignition allows the cap to remain visible. Do you?"
There is no requirement that the cap remain visible.
Ignition is to be wheel lock, matchlock,
flintlock, or percussion using original
style percussion caps that fit on the
nipple and are exposed to the weather.
"Exposed to the weather" means the
percussion cap or the frizzen must be
visible and not capable of being enclosed
by an integral part of the weapon proper.
Primers designed to be used in modern
cartridges are not legal
I guess I'm reading it wrong then!