A great deal of the appreciation for Bill comes from having read that first story. He's an alien warrior fighting to protect his fleeing people from a race of interstellar demons. He sacrificed his "humanity" ala' Rom to become their defender, and in the course of his ongoing battle chanced upon Thor. Recognizing that Thor was a mystical entity, he fought him, believing him to be some new form of demon and in so doing won the right to hold the hammer and possess the power of Thor.

He's worthy. And visually arresting. And he has a sense of humor. What's not to love?

Where the problem comes in is in depriving him of the mission that originally defined him as being worthy of the power of Thor. Without his commitment to his people's safety, he's not so interesting. He can occassionally be summoned to Asgard, per Odin's wishes, without great harm being done to his credibility (The King's shilling, the King's bidding...) but spending all his time with other Marvel heroes like the Guardians or Power Pack makes him simply the Bizarro Thor, and that isn't something the Marvel Universe really needed...

The appeal of Beta Ray Bill is that he's a Marvel Hero, as worthy and as mighty as any other, but his mission is so very far from the usual Marvel neighborhoods that he is all but alone in his war. An alien Thor, forever fighting for the protection of innocents in an alien Valhalla, occassionally finding solace in battle alongside his fellow Thor or comfort in the company of the Lady Sif.

Plus, it helps that Walt wrote him so well.

As for Dr. Strange, there are apparently compacts and arrangements made long, long ago involving the sharing of power when the names of certain, ancient powers are invoked. Raggadorr, Faltine, & the Seraphim showed up for the meetings. Odin apparently did not, else Strange would likely have called upon him before now. To suddenly have him begin doing so would smack of changing the rules midgame. Such changes are rarely if ever for the better.

Odin bequeathes his power as he sees fit, be the recipient alien or amphibian. To date, he's not seen fit to do so for Midgardian practioners of the occult, especially those who've studied in the East where the Asgardians were never known. There's no explicit reason, I suppose, why he couldn't suddenly do so now, except that mixing Kirby and Ditko that recklessly doesn't seem like an especially good idea.

Something about Strange's involvement with the Defenders strikes me the same way, as if we're attempting to mix pieces from different jigsaw puzzles into a coherent design. It helps a bit, I think, that an Everett character is in the mix to diffuse the effect.