How much should aspect invocations "retcon" the situation?

Question

Shortly, I plan to test a game based on Fate 2e (the self-contained rules set, available here) and the Shadowrun campaign setting, with slight modifications. There have been a few things troubling me about this. The first one is items, partially answered in the recent question, and the second one is invoking for effect.

A big part of Shadowrun is planning and money. So you have to think through the operation, and decide whether you will spend the money to buy a rocket launcher, for example, which you might need later.

However, a normal fate player could probably just get himself into a sticky situation and then say "i invoke my aspect preppy pyromaniac, so I have bought a rocket launcher earlier". I find this disturbing to what I imagine to be the classic shadowrun playstyle.

Am I wrong?

What's the generally accepted limit in this type of invocation usage?

Is there a problem in banning this type of usage? I know it will be less story driven, but can I still call it fate?

Is my concept even viable without losing the good point of both games?

Answer 1

Fate is more of a toolkit so you can use the tools in it to build game mechanics suited to your intended story atmosphere.

The major tools in Fate are: Aspects, Stunts, Skills, Stress tracks and consequences.

For your specific case, I'd construct a limiting mechanic using a new stress track for the whole mission. Let's call it the Budget stress track. Determine the number of boxes when you give the mission briefing. Anybody can use maneuvers as usual to equip themselves with some nice aspects proactively or retroactively as usual, but every time this involves equipment or other things that would require any spending, it also attacks the mission budget stress track.

If you blow the budget, then the GM gets to place a not-so-nice aspect on the whole mission that reflects the effects of a badly managed budget. "Yeah, you got the rocket launcher, but there isn't enough money now to buy the up-to-date security schematics from the black market so you're practically going in dumb and blind"

You may as usual invoke any available and sensible aspects to mitigate the budget stress, so having an Accounting wizard in the team may come in handy. You may even take consequences to reduce the hit on the budget, so maybe instead of the compact and lightweight advanced launcher, all you could afford was this archaic big bulky tube, so you're encumbered by big explosives on the mild consequence slot.