I agree about Man-Thing, but I always thought miniature/shrinking characters had virtually unlimited tales to tell. 

Just my view, of course, but if I look around my apartment, communal garden, street, city, etc., I see many hazards and challenges for a tiny character, whether it be trapping them in a park pond to face fish or being stuck in a washing machine. 

Two keep coming to mind that wouldn't make it without some substantial changes. I don't think that Angel or Professor X would be very good on their own.

That doesn't mean that a solo feature wouldn't work with a feature about a man whose powers are flying and some vague bird-ish traits, or a telepath... or even a man in a wheelchair.

But Charles Xavier just seems to work only in a team setting - which isn't a bad thing.

Similarly, I don't think the Angel is a good solo character. We all know characters whose only power is flight (winged or not) who can hold a feature... but I don't think that Warren Worthington III is one of those. There are very defined aspects to his character, but I'm not sure they all add up to a regular strip holding a lot of attention... unless, of course, his character was radically modified. Archangel might be a good book.

Also, I noticed something at 90s Marvel (and DC to a lesser degree) that I saw in late 60s DC comics. Characters of every name, type, power, smell, etc. got either their own ongoing or limited series. A metric crap-ton of X-Men, supporting characters, villains, etc.

I think about series like "The Creeper", "Hawk and the Dove", "Metamorpho", "Secret Six", etc. that DC put out for public consumption. This big difference is that a lot (not all, granted) got a tryout in one of DCs two "audition" books - Showcase or Brave and the Bold. Marvel had a lot of "feature" books that were like this, but I don't remember a lot of those post-speculator-boom Marvel titles that had try outs... it seemed like the House of Idea just flung #1s at the wall to see what would stick. So I guess the "unsalvagable" idea is a little different for a publisher...

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I would always defer to talented writers where possible. I just feel there are many opportunities for small characters. Almost every household item I can think of can be a death-trap for the likes of the Atom (toasters, vacuum cleaners). There's the pet cat, too. And a small communal garden like the one outside my apartment block is a "jungle" to the likes of the Atom. 

But I don't, of course, have experience of writing superhero characters so could be wrong. 

That being said... I'm not a comic writer. Messrs. Byrne, Simonson, Stern, Waid, etc. could likely make a very tasty pie out of Warren and his adventures.