As to those against adding vanilla to the launcher I can tell you guys have no sense of marketing branding nor common sense.
Please enjoy walking on train tracks and playing in traffic cause with your logic the cars and trains can just drive elsewhere.
Sigh.
If you want to try vanilla 1.5.x, try vanilla 1.5.x. If the only reason you want a snapshot in the launcher is to avoid having to use a second launcher (the vanilla Mojang launcher), then you
are lazy.
If you work hard all day and don't want to spend time getting a damn game to work - you just want to play - then use the FTB launcher. Oh, be thankful - there used to be no way around all that effort getting it to work. Now, it is almost one click.
If you want to take a snapshot and tweak it (or, as you first said, "I think there needs to be current vanilla minecraft (so players can tweek or check out the mods that are current"), then there is MultiMC. The FTB launcher makes it easy as possible to customize the FTB packs, but once you start tweaking, there's a better tool. Like I said, I recommend both.
I appreciate the efforts of countless people, including the FTB team. From what I can tell, they work hard to put these packs together to make it easy for us to come home from work, download, and play. There's a lot of tweaking and configuring and whatnot that went into that. I hope they keep working on the packs, the videos, the maps, and so on - all the stuff they do well. Hopefully through all that marketing, they are pushing the authors to be even more cross-compatible. I also hope that they are already testing and planning 1.5.x packs.
So, one final time, why? What advantage does a 1.5.x snapshot have? You said yourself, in the OP, that it allowed players to tweak. Those players should not mind grabbing an awesome second tool.
And then, you bitch about how you shouldn't have to "tweek" and go on and on about what you do for a living or some other irrelevant crap like some entitled brat. You don't have to tweak - don't you get it? Play 1.5.1 and shut the F up. Or play some FTB pack, and shut the F up. Did you know that it was easy to tweak the pack in the FTB launcher, like to drop in OptiFine or remove GT? Oh, I'm sorry - such a hard worker like yourself shouldn't have to tweak a game. Did you know it was easy to fine tune packs?
So please continue to point out that I'm like a suicidal hopscotch-er or whatever instead of answering the basic question:
What advantage does a 1.5.1 snapshot in the launcher offer to anyone?