There are many kinds of block explorers: some are just showing regular blockchain data, as they are handled by full nodes. Some are
UTXO-based, and focused on pruned ones. However, when I think about it, I guess we could need another kind of explorer: a signature explorer.
Blockstream's explorer can already show the signature of each input when you toggle "
Details +" button at the right-hand side of the TXID.
It's hidden by default since the information aren't meant and useless for regular users.
Check if out if it satisfies your use-case.