Don't forget that the repository entry for each flight can be wiped and space recycled at the end of each flight.
Three people have just spelled it out to you .....
Data storage would the cheapest part of the whole solution, infact it verges on irrelevant in the context of the other costs.
The main problem in terms of operational expenditure surrounds the use of satellite communications. Which isn't cheap, and will probably suffer from capacity issues if all airlines used it.
Pile the operational expenditure on top of the capital expenditure and you can see why your dream is destined to remain a dream. It simply is not workable from a financial point of view given the highly limited number of rare circumstances where it would be useful.