A bit late to the party here but I thought I would chime in.
In short, I agree with most of what MercilessMing says.
Perhaps the bigger, broader answer is to have a conversation with your players about what sort of game they wish to have. As a GM, I love sandbox campaigns where the world is alive and dynamic and the players come to me with ideas and we figure out how they play out and what the consequences are. Other players just want to sit back, turn their brains off, and react to whatever the GM throws at them.
So, step one: figure out what's fun for your players. My advice is to run with that, because that's where they will have the most energy and enthusiasm, which best keeps them engaged with the game, which gives the game vitality and a chance to really tell some stories.
Over the years I've seen every flavor of campaign, where the PCs are Lone Star detectives, to Doc Wagon medics, to corporate assets and problem solvers, to criminal syndicate members, to bounty hunters, to soldier-mercenaries, to hooding punks, to Infected on the run, to amnesia campaigns where the players don't know who they are. Now that we're sitting on top of 30+ years of lore, the Sixth World setting is more than broad enough to accommodate all those stories and many more. My favorite campaigns that I've ever run have been ganger campaigns, which are closer to what MercilessMing describes as "business tycoon simulator" games than a more traditional game about shadowruns, but they were wildly fun and gave the players opportunities to hatch plots, conduct diplomacy, form scatterbrain plan, to generate revenue, etc.
Circling back to the original question(s), my answers are similar to MercilessMing's:
1. This is awesome, a perfect foundation for a session, and I would run with it.
2. Yes BUT... consequences. Again, very similar to what MercilessMing outlined. Congrats, you made a bunch of money! But, oh, it's all on paper and now the feds would like to have a word...
3. Yeah, just what Ming said. Or, you know, let it work! But having it work paints a HUGE target on the players. The original owners of Project K are displeased and have something to say about it. Now the players have to burn through the nuyen they earned just to stay alive and one step ahead of a seriously pissed-off corp.
As an aside, my general experience is that a significant amount of nuyen does not break the game. If anything, it can often inject new life into it, making things less predictable. If you've been running for a while, it can break you out of routine and give the game fresh legs. Plus, if you have gear-intensive PCs like riggers or deckers or samurai, it can help them close the gap with the adepts and mages who can improve by leaps and bounds simply through karma alone. I've dropped six-figure paydays on my players before and found that it didn't really affect things nearly as much as I thought that it would. I once received a seven-figure payday and in my opinion it really took the game to new heights. I applaud the GM for being brave enough to do it.
As Ming says, don't give them the money for free, but if they earn it - either through intrepid entrepreneurship or through horrible horrible consequences - then I say go for it!