No its a extremely huge problem. People don't know *which* fork will be validated later on, the transaction from the destroyed fork will be invalidated, and will never get confirmed in the chain that survive.
What will everyone do if that happen? They will dump it down to 10 cents in one hour.
why not? as i said they are already signed and miners can just pick them up
No they can't. For example block X get mined on fork #1, it include XYZ transaction, that fund then get used later on, its on block X2.
Meanwhile the same happen on Fork #2, the same block has been found by someone else and fund are already moved are spent on fork #2 and it include different transaction. All those transaction can't be validated since the funds cannot be used twice. And destroyed transaction aren't returned to the mempool to be retried.
Instead the block chain repair itself and after the forks return to one chain, every fund that was spent on the other (destroyed) chain will be back to where it was when the fork happened.
Which means no one can put FIAT value on it since they don't know if the transaction done at the time will be validated.
that is only true if some party tries an malicous doublespent. in that case you are right.
but you should not assume that all bitcoin users are thieves. in case of a large split exchanges and other services will find ways to detect that (which probably means way longer conf-times on both chains than we are used to atm)
edit: btw this assumes that someone is able to broadcast a tx in both forks. if there is an internet connection between two forks there will be no fork at all
No... you don't understand;
Both fork will find the same blocks for a while, there's nothing to rebroadcast, you can't rebroadcast that you actually own all those BTC, because you just dont.
Only the chain that survive will decide who really own those blocks, which means from the destroyed chain, every blocks found, its fund and its and transaction included in and after those blocks will be completely invalidated and its completely impossible to rebroadcast those transactions, since the owner of those blocks will have changed;
The people people that found blocks and did transaction after the fork will see all of their actions reversed. You can't have a block reward twice, once for each fork.
Its just not.You can have the wallet rebroadcast all the transaction and IF they had the fund
before the fork, then sure they can then be accepted but that doesn't matter because at that point BTC will have crashed to nothingness because of the primary effect.