Most of them, if not all of them, work the way they are already but what songs could have worked as alternate openers?
For example...

Daddy Pop instead of Thunder mabye?
Uptown instead of Dirty Mind?

Endorphinmachine could've worked as an opener to TGE. I much prefer it to Pussy Control. Though with its opening lines i guess it was designed purposely as an opener.

IMO,everything is perfect as it is. Prince makes great choices!

it sort of was the opening track to disc II of crystal ball but still,
"Interactive" would have made a great opener for 'The Gold Experience'
or even 'Come'.

i still think "20/20" would have been the perfect way to open up the
first disc of 'Emancipation' -an alternate less generic emancipation.

"Graffity Bridge" could have done with another opener, although i've
always wondered what song would be suited. perhaps the best candidate
would be "Elephants & Flowers" since it puts the message of the whole
project out there.

also 'Mad Sex' would have been a nice opener to "New Power Soul" cuz
it kind of sets the mood for a laid back off guard funk album with a
mellow pulse and some self mockery.