I know this isn't entirely realistic, and a lot of people will argue that this is only possible in a video game, but I think these are fair trades that should draw some interest.

The following things would have had to happen by the end of the 2008 season:

Trade C Yadier Molina and SP/RP Ryan Franklin to the Rays (who desperately need a catcher) for SP James Shields.   Shields is a 26 year old righthander who put up a 3.85 ERA last year, and the Rays could use Franklin as a stopgap either in their bullpen (which is horrid) or the back of the rotation.  With Wade Davis, Jacob McGee, David Price, Jeremy Hellickson, etc. along with Scott Kazmir and Matt Garza, Shields is expendable to the Rays.  Bring up C Bryan Anderson to replace Yadier Molina.
Anderson hit nearly .300 (without much power, though) as a 20 yr. old in AA.  He is a very solid defensive catcher, and there is not as big a difference between his arm and Yadier's arm as some people think.

Bring up Jarrett Hoffpauir to play 2nd base.  Between AA and AAA, the 24 year old hit .324 with a .407 OBP and a .473 SLG.  He had a spectacular 55 BB to only 39 K.  Although he doesn't have more than average speed, Hoffpauir's on-base skills are tremendous.  

Colby Rasmus would be the starting centerfielder.  There's not much to say about him except I think he's possibly a Grady Sizemore type player.  

Now, trade utility IF Brendan Ryan and Scott Rolen for 3B Andy LaRoche.  The trade talks for LaRoche have been on and off for quite some time, and he's been wasting away in AAA for the last 2 years.  As a 24 year old, he slugged nearly .600 in AAA last season.

Now your needs in the field are a SS and 2 corner outfielders.  I would keep Cesar Izturis around, since LaRoche isn't a good fielder, and I can't imagine Hoffpauir's range is spectacular.

Next, trade Chris Duncan to the Indians for SP Jake Westbrook.  The Indians have a glut of mediocre outfielders (Delucci, Shin-Soo Choo, Michaels, Franklin Gutierrez) and aside from Grady Sizemore, the Indians don't have a lot of stability here.  Westbrook seems like a pitcher the Cardinals would be interested in.  I imagine with Edmonds and Rolen coming off the books, that the Cardinals could pick up some of this salary.  

When the 2008 FY Player Draft rolls around, we'll have the #13 pick along with a compensation pick (somewhere around 40th overall) for losing Troy Percival.  It's far too early to pick out a specific player, but I think that I'd be looking for a college pitcher with the #13 pick, a high school corner outfielder with the supplemental pick, and another college pitcher with the 2nd rd. pick.  I could see the Cardinals selecting Tyson Ross from UCalifornia (a command guy ranked #17 on Brewerfan.net,) but I would prefer to take LHP Christian Friedrich from Eastern Kentucky or RHP Jacob Thompson from Virginia.  Friedrich is more impressive in my opinion - a lefty with a huge curveball and great arm action.  

Hopefully Friedrich could progress through the system quickly - it's possible that he could be in the majors by 2010.

I'd keep backup catcher Jason LaRue around (no reason to change.)

If David Freese made progress in AA, he would probably be my backup 1B/3B by 2009-2010.  For now, Scott Spiezio will stay put.

As bad as Adam Kennedy is, he couldn't get any worse.  He would by my backup 2B in 2008.  

One problem would be dividing up the playing time in LF and RF between Ryan Ludwick, Skip Schumaker and Rick Ankiel.  Spring training would play a huge factor, and these guys would have some type of platoon going in 2008.

The biggest questions for the beginning of 2008 are who will play where in the OF.  I would let Brian Barton start in CF at the beginning of the year, and hopefully hand the job over to Rasmus in the second half.

The hitting portion of the team would look like this by the offseason of 2008-2009.  

RF Skip Schumaker (predict a -280-10-50 season)
2B Jarrett Hoffpauir (predict a -290-10-60 season)
CF Colby Rasmus (if he played the entire year, a .275-25-90 season)
1B Albert Pujols (.310-40-100 season)
3B Andy LaRoche (hopefully a -290-20-90 season)
LF Rick Ankiel/Ryan Ludwick (-265-25-90 season)
C Bryan Anderson (-270-10-50 season)
SS Cesar Izturis (-250-5-40 season)

The bench:
C Jason LaRue
2B Adam Kennedy
3B Scott Spiezio
OF Brian Barton
OF Ryan Ludwick/Rick Ankiel

I would imagine this team could hit somewhere around 160 home runs on the optimistic side of things.  Any way you cut it, 2008 is going to be a rough year.

I wouldn't try to do anything to drastic in the beginning of 2008 pitching wise.  However, by the end of 2008, the rotation would hopefully look like this:

SP Adam Wainwright
SP James Shields
SP Jake Westbrook
SP Joel Piniero
SP Braden Looper

I don't expect Mulder to be anything near what's considered effective, and I assume Carpenter won't be playing until the start of 2009.  I don't have a lot of faith in either of them, so I left them off.  It Mulder did come back strong, He would bump the 5th starter off.

Jaime Garcia solidified himself as the best Cardinals pitching prospect last year, and I really think he could be a dominating lefty.  He's only 21, and I'd see how he does in AAA next season.  He'd replace the odd man out.

Here's the bullpen:

The bullpen would consist of Tyler Johnson and Randy Flores as the two lefties, Brad Thompson as the spot starter/long reliever, Russ Springer as the SU, and Jason Isringhausen.  A combination of Parisi/Motte/Wellemeyer/Worrell would fill out the rest of the bullpen.  I would REALLY push for Chris Perez to be the closer for 2009, making Jason Isringhausen expendable.  

Hopefully, RHP Mitchell Boggs (who had a solid year in AA last season) would progress toward AAA.  Perhaps by 2009 he would be fighting for a back of the rotation job.  

At the end of 2008, I imagine Carl Crawford would be a free agent.  I would do whatever it took to put Crawford in a Cardinals uniform.  I would let Mark Mulder walk for $1.5 mil.

I would trade Isringhausen to a contending team that needed a closer (since his contract is up at the end of the year, anyway.)  Last year, Scott Linebrink netted the Padres Will Inman (whom I think a comparable comp. would be Jaime Garcia) at the break.  Perhaps the Indians would be in contention and would need help.  One player that I would definitely trade Isringhausen for is OF Nick Weglarz.  He hit .276 with 23 HRs and an 82/129 BB/K ratio last year with Low A Lake County as a 19 year old.  

So now, you're looking at this type of team for 2009:

C Bryan Anderson
1B Albert Pujols
2B Jarrett Hoffpauir
3B Andy LaRoche
LF Carl Crawford
CF Colby Rasmus
RF Skip Schumaker

Bench:
C ------ (whoever)
SS Tyler Greene
3B Brian Barden
LF Rick Ankiel
CF Brian Barton

SP Chris Carpenter
SP Adam Wainwright
SP James Shields
SP Jake Westbrook
SP Jaime Garcia
Spot Starter/LRP Mitchell Boggs
RP Mark Worrell
RP Tyler Johnson
RP Randy Flores
RP ----
RP ----
SU Russ Springer
CP Chris Perez

Keep in mind, you could potentially have Adam Ottavino, Tyler Herron, Nick Weglarz, Christian Friedrich as your top 4 prospects in the minor leagues, so you still have a fairly decent system to fall back on.