Allow URL parameter to pull in email preference form

I'm having issues with our email preference/unsubscribe forms not pulling up someone's correct information. Currently Marketo forms work on cookies, but if someone is not cookied, or cookied under an alternate address, they aren't accessing their pref center appropriately and this is a big issue for CANSPAM compliance. I want to be able to add ?email={{emailaddress}} to a form (or better yett {{lead.id}} so it's not passing PII) and then have that form populate according to the corresponding unique identifier in the URL parameter. This is how most ESPs have worked and I'm a little uncertain why Marketo does not have this offering.