It's not as easy as you think.
As an example look at this transaction:
https://blockstream.info/tx/a697ea66639ba7966269e935d4374e28bc368ca683c7214dfc28e42eae026ddeblockstream has a pretty basic privacy analysis:
* Round payment amount
* Mixed script types
* Unnecessary input heuristic
which suggests the privacy of this transaction is quite poor. However, it could actually be excellent! I have frequently hand-created transactions that look like they are doing something obvious (e.g. this transaction looks like it's a payment to the 0.3 BTC output) but in fact, that 0.3 BTC output might be the change output! (thanks to careful coin selection/mining fee) and maybe the 0.021026 BTC output is actually the payment. The absolute best transactions from a privacy point of view look like one thing, but are doing the other.
So to create a real "privacy score" you basically need to know "what it looks like" vs "what it actually is" on a wallet level (?)