I think a Michelle/Beth feud will happen eventually, but for now the WWE are just teasing it - similar to how they where been teasing a Michelle/Mickie feud before the diva trade even occurred. Would I like to see a Michelle/Beth feud though? A few matches here and there, yeah, but certainly not a full blown women's feud between the two. Neither have the charisma or crowd support to pull something like that off, and there lies a problem. Michelle can't talk on the mic, and she's about as dull as a red brick house when it comes to making herself exciting in the ring - that's not to say she's a bad wrestler, because she's a phenomenal wrestler who could give some of the guys a run for their money if she wanted to, but she lacks a special something that actually makers her exciting to watch. As for Beth Phoenix, she's lacking in the charisma dep too, and personally I don't find a women dominating matches the way she does appealing, it's spot-after-spot, and generally relies on the opponent doing the work by selling the offense and making Beth look great. Although that being said, McCool and Beth are dominating wrestlers these days when they're wrestling, so maybe this could be one Phoenix match which is actually 50/50.
If they where to have this feud, they've got to get at least one of them over as a heel or a face, or the crowd won't give a dime. They can give as many titles to McCool, they can have her be the longest reigning champion in the WWE (which she currently is), they can have her hold the first two womens titles in history, it doesn't matter, it's not getting her over. Beth Phoenix has received protected monster pushes, and it barely got her anything other than titles - like with McCool, doing that won't necessarily get you over.
Don't get me wrong, I'd genuinely love to see these two square off in the ring because we've not seen it before, however there are just one or two flaws that may possibly make this feud boring. Should WWE hold it off? Yeah, definitely, until McCool can finish her feud with Mickie, then actually get some heat. After Mickie has (or if) gets the belt, i'm not expecting a Beth/Mickie feud. Natalya is out there waiting for something to do other than be a female mouth piece for the Hart Dynasty, there's a world of opportunities out there for her, if she can feud with the right face over a title.
A McCool/Phoenix feud will happen somewhere along the line, it'll be interesting to see how the match itself goes, will Beth dominate and McCool will be left to dot he selling? Who knows. If anything, it seems like they're holding off Nattie/Beth more than anything. Personally that would be a womens match worthy of being on the Wrestlemania card, it'll be no Trish/Mickie that's for sure. However, if Mickie gets the title now, she can feud with Nattie, who will win the belt in the end, then she can go and feud with Beth. That seems to work for me, the only problem is McCool will have nothing to do, although I suppose she can put someone over in a sub-feud, possibly FCW's Savannah.