It cannot be denied that Flick has sufficient experience to make him worthy of being Barcelona coach. However, just like Xavi before, he will face no small challenges. Finances are quite a big challenge for coaches because they have to think about who to overhaul, sell, keep, etc. with quite challenging funds. So this is often the problem that Barcelona must be quite careful in determining the purchase, sale and arrangement of players and tactics.
With the new deal that Barcelona is signing with Nike, they'll receive 100 million now and 120 million every other year for the next 10 years as signing bonus, that should clear them a bit and allow them space to sign players.
However good Flick may be, he needs players. Players that fit into his system. Barcelona already have some quality players so a few signings may do the trick. If Barcelona doesn't back up Flick with the kind of players he needs, he'll struggle.
The hard decisions have to be made when it comes to the players to be sold. Players that are surplus to requirement have to be sold so they can free up space for new arrivals.
This summer should be very busy for Barcelona and what they've gotten right is appointing Flick on time. So now he has the time to arrange his team himself instead of walking into a team when all the transfers have already been made.