Hello,
I was thinking why bitcoin transactions are not separated from mining blocks?
If it's only signature thing (public/private key to show you are owner of bitcoins) then why not put them outside blocks to make them "instant" for people and leave mining as it is now?
Why "secure" transactions by mining if it is (it is?) only cryptography thing? Mining of course must be done as it is now due to "proof of work" stuff (finding proper hash), with a new "source" keypair generated for each block.
It's just an idea. I am 99% sure i am wrong, but maybe?

EDIT: posted in wrong place, please remove