Thanks for your input Hamed.T, always refreshing to get these kind of tips (and good reviews)!
Regarding deferring CSS & JS; for CSS this might cause "Flash Of Unstyled Content" which I presume most Autoptimize users would appreciate. JS is another issue; there "defer" might indeed make sense, but given that Autoptimize places the link to the aggregated script-file at the very bottom of the HTML, the gains will probably be minimal. Testing this is on my to-do list though, so it might indeed be added if it proves helpful.
As far as CDN is concerned; I will make sure to provide some guidance on how to switch to alternate solutions when that functionality gets removed from Autoptimize.