Automotive Switching Problem

[Accident94]

g'day all.

i'm mid way through an attempt to wire spotlights into my car. i want to use the stock switches, but they are not what you would call a simple thing to understand or use. i mocked the switch up in LTSpice, and have added, in MS paint, approximately what i would like it to do. (left of pic attached)

Basically, it's a non-latching momentary switch that shares a common ground with an indicator LED and a backlight LED. i believe it also switches to ground. i want that momentary switch to toggle a on on/off switch, which is then fed to the 12v automotive relay AND back to the indicator light.

i have just recently (like as i type this) figured out that i can, if necessary, adjust the internal electronics of the switch so that the switch is completely independent of the indicator LED and backlight (diagram on right of attatched pic)

i'm a bit stumped. i would have thought that my recent revelation about the switch would make it simpler, by dint of not having to deal with the switch-to-ground bit....
what remains is how to get a signal from the 'on' state back through the indicator light that shares a ground with the backlight that is on another circuit entirely. that, and how to turn the momentary power supplied by the switch into a constant on/off state toggled by the momentary switch that can then be fed into the automotive relay

cheers for any help in advance,
Matt