Will be interesting to see if the Camusnagaul (to Ft William) ferry frequency is increased to cater cyclists wishing (very sensibly) to avoid the A82 from Corran to Fort William. Otherwise your timings have to be assured to avoid an up to 2 hour wait.
As far as suitable types of bike is concerned, most of the route is OK for road bikes, and for the sections that aren't, there are sensible road alternatives which add little or no distance, or are shorter, but you'd need to be comfortable with cycling on the A82. The sections on the Caledonian canal towpath are excellent - good enough for an off-tarmac TT!
To get to the start, ferry to Cambeltown (from Ardrossan) is summer only, Thu, Fri (arr 9.20pm) and Sun pm only. It's a 3 hour trip, lovely for that and right down the Kintyre peninsular. An alternative I'd prefer is to go via Arran (from Ardrossan) and enjoy that island (either over 'The Struggle' or via Corrie, hitting Kintyre at Claonaig(summer)/Tarbet(winter) and heading north.