What no interest in the wooden sailing dinghy? Good it’s only useful a couple of times a season.
I’ve had owned an all wooden, all fiberglass, RIB (inflatable with fiberglass bottom), and currently a Zodiac® inflatable (inflatable keel), and wooden floorboard inserts. I seriously looked at the inflatable floor and was dissatisfied with the amount of space you loose in the sole of the dinghy (as the floor inflates it rises and you seem to loose 2-3 inches of depth in the dinghy sole, therefore I opted to wooden slates and about 20 lbs of weight that they added.
I believe the a 9 foot dinghy is ample for 4 people and light enough for 1 person to bring up and down, or in and out of the water.
Propulsion…do you want to plane your dinghy or just motor to the dock? If it’s the former 8 HP 4 stroke minimum, if it’s the latter 3.3 HP 2 stroke max. 2 stokes will need more TLC than the 4 stroke, but they’re lighter and will offer the engine mounted tank you desire.
Before you buy take some time to comb the lee shores of the bay for any runaway tenders.