It looks like its possible to use something like granary (https://github.com/snarfed/granary) to create basic profile cards that display an avatar/bio/recent tweets etc. for @user@twitter.com links
heres my mastodon atom feed: https://haste.tchncs.de/otiyalakic.xml
and heres one for twitter: https://haste.tchncs.de/sequradoru.xml
https://github.com/tootsuite/mastodon/issues/1849 is a relevant github issue
Once I get a better grasp of it all I'm going to create a mockup of how it could look.