Doing this benefited Whedon in one obvious way already. #16 makes it so that 'vampires in public' makes sense for Season 8. Now recall that quote that upset some After the Fall fans:
Scott Allie: The main reason Joss provided the outline for After the Fall was so Fox would give us unlimited permission to use any Angel character we wanted in Season Eight. We just haven't had cause to use those characters yet, but we will use some at some point. You wouldn't call it a crossover, though, I don't think.
The key word there being "unlimited". By Joss paying dues in working on After the Fall, it's almost like he bought back certain characters that went over to AtS. The one character I'm thinking of being Spike. But another character has been noticeably absent from any mentions of Aftermath and has not been mentioned in a spinoff - Illyria. Who happens to be one of Whedon's favorite characters according to a recent comic-con.
Did Joss make a deal to get back characters he wanted to work with? Remember how much Allie regretted selling the Angel license to IDW - perhaps that regret was because Whedon had plans for certain characters in conjunction to Season 8. Apparently the license applies to making comics with the titles and characters, but that Allie and Joss found a loophole where if he contributed to the outline of After the Fall, he'd get back the rights from Fox so that Dark Horse can "use any Angel character we wanted in Season Eight." The lack of Whedon's name on Aftermath should show that it was a limited time offer - he contributed and gave his name and now it's over. I'm getting the feeling he's both too busy and not as interested in steering the story of Angel (many would argue he never has been that involved barring AtS Season 5 - my fav season btw). I think it's clear that Angel is off on his own and he has been for years.
Could Joss be wanting to bring Spike and his new buddy, Illyria, for some playtime on Season 8? Presumably, only for the "big moments." I know a lot of people felt that Spike was a perfect fit for AtS and he gelled in that environment, but it seems like he's disappeared from the playlist for Aftermath and no spinoff is in the works. The thing about Spike is that he had one year on AtS versus being on BtVS ever since the 16th episode of the series. He also played a pivotal - no, I'll say crucial role (no matter what Stormwreath's recent analysis of Chosen says ;)) in defeating the Turokhan army and closing the Hellmouth in Chosen. And Season 8 is about exploring the consequences of Chosen and how the world has changed - who better to show Buffy and Co. how they've strayed than an old ally who could clearly see the differences? Season 8 is about where we go from Chosen and in that sense, I can see how Spike would fit with the future story. He's the living embodiment of the 'before picture' for Buffy and the gang. What's more, he's always been the one to tell them off when he disagreed with them. Perhaps Spike might notice some disturbing similarities between S8 Buffy and S5 Angel - and Spike saw firsthand how well that went.
And really isn't that what's missing from Season 8? We've lost the Cordelia/Spike/Anya of the group who told them they were messing up or acting stupid or self-involved. There's no one there to tell them they're losing the mission - perhaps there will be in the future. I'm not saying that Spike is coming back to his roots for good, but that he'd work well for a future visit.
This could all be made moot by a Spike/Illyria spinoff being announced post-After the Fall #17 where Angel and Spike have their talk about Spike's future plans. But we do know that Joss will be using some characters from Angel in Season 8. Probably towards the very end. I'm betting Spike's ticket has been punched for that.