I recently discovered this:
Kicker Subaru Tweeter Upgrade for 4runner?
Looking at pictures of the subaru kickers in question compared to the factory tweeters in non-jbl 4th gens, betray key similarities and differences.
5th gen tweeter connector is attached to the tweeter, 4th gen is on a wire lead.
Both tweeters appear to have a similarly-sized capacitor in approximately the same place.
Anyone think there might be something to this for the 4th gens? I'm thinking possible depth issues (mostly do to the plastic cup underneath the kicker tweeter, and the positioning of the connector), and I cant tell if the connectors are at all similar, but I think it might be just a kind of cut-and solder to have plug-in tweeter replacements.
Amazon listing for the subaru part:
Amazon.com: Genuine Subaru H631SFJ101 Tweeter Kit: Automotive