I can't believe how in love with that island I am.
You need to try some other islands next ... how about a few days on the Outer Hebrides? Catch a train to Oban, ferry to Lochboisdale, and keep cycling NNE-ish (with lots of wee side-roads to explore off the main road) ... ferry back from Stornoway to Ullapool, cycle to Garve (or Inverness) and catch the train back - a bargain with the CalMac Island Rover (you only need to remember to pre-book your bike on the trains you want to catch, due to the limited spaces available on the two train routes involved; ferries no problem).
Closer to home, Bute is great, too - with some good hills (including the Serpentine in Rothesay), but a lot flatter overall than Arran, and very quiet roads... We spend a weekend on Bute, exploring all the roads and sights - but it would make an equally good day trip with lots of loops and dead end roads - all of which are leading to or from Rothesay and the ferry
Back on topic ... looks like a big CC Ecosse Peloton is forming for 3rd August
T