I'd love to see a 78 set.
Just a word of caution. Doing the classic rosters is really a labor of love. It takes forever to edit a team if you want to get height/weight close to being correct, skin color, equipment, and player ratings. Doing one roster for all 32 teams can take a month or more...and that is if you work on them daily for a good part of the day. You also need to "play test" each team to ensure that the players play as you would expect, and adjust ratings as necessary. Just as an example, editing one existing player to an older player takes about 3 minutes or thereabouts if you have all the info beforehand. Does not sound like much but with over 1500 players in a roster set that alone comes out to 75 hours of work...and that does not take into account any of the other items I mentioned above (CAP, free agents, play test). If you have a job, family, and any type of life it will take weeks for one roster set at a minimum.
You will find yourself having to edit some existing players which you can use for close matches to older players, but you willl also need to use CAP to create many players. Then you run the risk of hitting the CAP limit. Also, you will need to sign free agents to your teams in order to get the proper player matches and you have to deal with salary cap concerns when you do that. So, a lot of thought goes into creating each team if you do it right. It is a real PIA!
I hope you pull it off. It would be great to see different seasons. I just wanted you to know what type of work you will be undertaking.
C