I like this idea in all but the combined mode part. I treat Transformers based on their fictional "sentience", which also comes from the names / tech specs / etc provided to them by the manufacturers. For example, Reflector. They each have separate robot identities, and are each independently sentient. This is as opposed to Optimus Prime, Roller and the trailer, which are not independently sentient, or pretender shells.

I have chosen this method for the reason that Transformers are , at the manufacturer's behest, "Robots in Disguise". They do not need to have an alternate form to continue to be a sentient robot, even though the may need to get their friends together to disguise themselves.

The exception I have here is Nebulan partners (which came with the toys) as they are accessories and not robots (using the US fiction as stated by the manufacturer on boxes, tech specs, etc).

While I understand griffin's proposal to base the collection count on "toys" as physical products, and believe this to be very valid, I prefer myself to base it on the sentient robot modes (or characters) which is how the figures are referred to by the shows, manufacturer tech specs, and fits into the "Robots in Disguise" concept.