I don't think running 318/320 in Ayrshire will work anymore if the DOO monitors aren't there.
My speculative ideas of potential service levels without the 380s:
2tph to Ayr all stops with 156s, with buses from Kilwinning to Ardrossan/Largs
2tph to Gourock all stops with 318/320/385
1tph to Wemyss Bay semi fast with 318/320/385
2tph to Paisley Canal with 318/320
2tph to Neilston with 318/320
2tph to Newton with 318/320/385
As said above, running more 334s on Argyle to get enough stock to run the services etc