Regarding the Invaders...NO!  Sorry, just not remotely interesting to me personally.  Back in the 80's this might have been an option.  Alpha Flight...HELL YES, but...Byrne has expressed no further interest in those characters that he helped create...such a shame...A VERY, VERY SAD SHAME.:( 

Something brand new and unique would make more sense to me.

-C!

Any form of Captain America or an X-MEN: THE HIDDEN YEARS would be thrilling too. Heck, any story that needed to get out of your head in any titled format would be my what if.

I think that a Kid Colt series would be fun to see. If not him then maybe the "marvel" version of Wyatt Earpp that was published in the 50s. Might be fun to explore the old west version of the marvel universe. 

If we want to get cosmic I would like to see a series about Galactus. Not the Last Galactus series but a series focusing on the years before the fantastic four. There must be billions of years worth of stories from when Galactus was devouring worlds before the FF. It might be fun to see his time when the Silver Surfer was his herald or when Firelord was. There must have been other worlds that tried to stop him. Could be cool.

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ARE there teams anymore?  There are writers (who never seem to leave a book, and who never seem to want to do the iconic version of the character/team) and there's a revolving door of artists on almost every title, swinging in and swinging out almost every issue.  (Maybe worse at DC, where every issue is done by three to five artists.)

Not to fear about displacing any team, Mr. Byrne.  If they really want you on a book these days, they'll just do a new number one and add a new adjective--"The Indubitable Hulk," "The Indredulous Iron Man," "The Uncanny Spider-Man," etc.

Sorry, don't mean to gripe TOO much!  I'm enjoying this thread!--  and some of the more out of the box suggestions like MACHINE MAN and CONAN!  And the THING team-up idea!  If not MARVEL TEAM-UP, then a new MARVEL TWO-IN-ONE would let you get around to EVERYBODY--and the THING on a regular basis!  (Or can we have a SHE-HULK TEAM-UP?)

JB, by realistic I assume you mean something that has reasonable sales. From a marketing point of view, your return to the House of ideas should be done with characters you're most closedly associated with or characters that have become more widely recognized through the recent MU movies, not some forgotten characters from the '70s only old fans care about or some new creation no one's ever heard of. 

Also, I think it would be better if you did some "stand alone stories" or "prestige format" books similar to what you've been doing with Star Trek New Visions at IDW instead of a regular ongoing "standard format" monthly series. I'd also suggest that even if you do stories set in the past you should avoid going "archaelogist" and try to explain missing holes in continuity and that sort of stuff.

Here's  a few (hopefully) realistic suggestions: 

- a Wolverine graphic novel or mini-series. Correct me if I'm wrong but you never wrote the book back when you drew it. Surely, you must have some further tale(s) with this character and I'm sure it would sell because it's Wolverine AND JB. 

- a graphic novel or mini-series featuring the new X-Men from the classic Byrne/Claremont/Austin era after the Dark Phoenix Saga: Storm, Wolverine, Nightcrawler, Colossus and Kitty Pride. Please, no Cyclops, no Phoenix, no nonsense. Just a new story using those characters. Fans would love it. Again, a sure seller.

- the already mentioned Fantastic FourEver project. Just more adventures of the classic team as if you'd never left. Inked by you.

- The Last Galactus Story Finale. Inked by Terry Austin. Colored by Glynis Wein. Original ending, no FF, no Doom. Nova should've been the next Galactus. Make it as seamless as possible to the previous chapters, like you did with JBNM. Afterwards, Marvel should have it all collected into one nice large format volume.

- Captain America in WWII. The Invaders could be part of the book, sure, as could the Howling Commandos or the Liberty Legion, but Cap has more of a brand name to make the book recognizable and marketable. Maybe Roger Stern could come along and help you out.