Simon,
I had a Coaster and sold it after one season. It was as you say.
Worst for me was that it was unusable for Raids due to the small cockpit and the poor rowing. Also didn't work with the dog in the cockpit.
I recommend not to save up & wait the BayCruiser, better get the cheaper BayRaider straightaway and make that comfy for casual overnighting. The Raider has huge dry storage under the hinged side benches for tent, air mattresses, cooker and overnighting stuff, plus huge space under the foredeck. Do order the sprayhood, that alone is already half the rent. For overnighting, you bring the gaff yard down horizontally over the cockpit, it is long enough to bridge the gap between main mast and mizzen mast. Over that you can -simplest and cheapest solution) spread a simple ready-made rectangular tarpaulin from the DIY store, with four small sandbags in the corners (or tie the oars as weight) which hang outside the hull. For complete comfort and closing to aft you can cut a single slit in the tarpaulin for the mizzen mast, and that will close the tent to aft.
For inside, you just need to cut two short pieces of plywood to bridge the width between the side benches (These pieces too can be stored in the side compartments) and then you have more than ample beds for two adults. You sleep with the feet to forward.
Additionally, smaller children could sleep on the floor in the aft end of the cockpit, but for more comfort you would just need some more plywood slabs to make two more extra large beds there. Space is there enough.
But once all the overnighting stuff has been taken down again, and disappeared in the lockers, the BayRaider has again full standing headroom, and that is what we like best and use 99% of the time.
Hope this helps your decision.