The reason StarCraft and WarCraft have similar storylines is because they should. Their inspirations, Warhammer 40k and Warhammer respectively followed similar storylines, and you'll notice a LOT of similarities between the games if you look closely. Honestly, I wouldn't be at all surprised to find parables between StarCraft and WarCraft given time and installations.
Faith come from the quality of their titles. WC1 and 2 set the bar for RTS at their release. Starcraft was undeniably THE best RTS upon release, Diablo was one of the most unique and awesome games ever upon release, Warcraft 3 once again raised the bar in the RTS field. They keep one-upping themselves, not to mention the competition.
And Lost Vikings would be neato.
That's all kinds of stupid, illegal, and impossible that I don't think I even want to try and cover. Besides that, the CnC3 engine would be horribly inadequate and stupid to try a Starcraft port to. Think more Dawn of War with HEAVY HEAVY modification, if anything. (irony, really).
You have no idea. Your imagination could come up with all kinds of ideas, but I'm sure your (as we have all seen before) puny imagination is no match for the likes of blizzard. Honestly I trust them with the storyline a lot more than I'd ever trust you to think up any storyline/gameplay/anything. You saying it'd be a "dismally failing disappointment" is like SF_Gold saying any star wars game made today would be a "dismally failing disappointment". So forgive me if I take your word for...well...what it is. That being worth ****.