One major way I see the GB attachments being used is in FP swap threads. On such threads, it would be more helpful if the amount of FP donated at the time never changed.
At the moment
Player 1 posts his ToB to have 5FP. His ToB shows 300/380
Player 2 adds 5 FP to the ToB. Player 1's ToB now shows 305/380 on all posts, everywhere.
Player 2 posts his LoA to have 5FP. His LoA shows 65/290
Player 1 adds 5 FP to the LoA. Player 2's LoA now shows 70/290 on all posts, everywhere.
Player 1 posts his ToB to have 5FP. His ToB shows 305/380
This is problematic. It doesn't make anything worse than it has been for a long time but doesn't help, either. On swap threads there is always the potential for cheating:
Player 1 posts his ToB to have 5FP. His ToB shows 300/380
Player 2 cheats and does not add 5 FP to the ToB. Player 1's ToB still shows 300/380 on all posts, everywhere.
Player 2 posts his LoA to have 5FP. His LoA shows 65/290
Player 1 adds 5 FP to the LoA. Player 2's LoA now shows 70/290 on all posts, everywhere.
Player 1 posts his ToB to have 5FP. His ToB shows 300/380
Players can not generally recall every detail of every GB (in every world). Spot-checks help but there are cheats (and the clumsy) out there. By keeping the donation/level requirement fixed at the time of posting, the incidences of fraud/error will dramatically reduce. So:
Player 1 posts his ToB to have 5FP. His ToB shows 300/380
Player 2 cheats and does not add 5 FP to the ToB. Player 1's ToB still shows 300/380 on the previous post.
Player 2 posts his LoA to have 5FP. His LoA shows 65/290
Player 1 adds 5 FP to the LoA.
Player 1 posts his ToB to have 5FP. His ToB shows 300/380. Immediately, it is clear that Player 2 did not add 5FP because the ToB should be at 300+5=305.