I have a related question: is anyone aware of any sort of online database for unaired pilots? Or pilots that did air but never went to series? I can imagine it would be useful when indexing here.

That helps, though it being Wikipedia some might not treat it as a verifiable source. I recently discovered that Vincent Terrace the TV historian has published several volumes listing aired and unbroadcast TV pilots. The books are hellish expensive but that's the sort of resource. I agree with the OP's suggestion of a sub-category for pilots though it might require discussion as to what to include and allow. For example, some pilots have been retooled as movies (random example: Manchester Prep had new scenes filmed and was released as Cruel Intentions II). Some have not been officially/legally shown but have turned up on bootleg VHS or DVD or online. Some are nonexistent: for example, the script for the pilot for a mid-1960s spin-off of Doctor Who was published by its writer Terry Nation about 25 years ago; no evidence it was ever filmed, but someone could potentially enter it anyway.

There is quite a lot of Dr Who poss related (Nation's problem was he retained rights to Daleks rather than assigning them to the BBC , which was clever but it meant for money he was chasing Dalek spin offs and inventing more space adversaries).