The major issues for flick would be the fact that Barcelona themselves are almost entirely broke and for a club like Barcelona that wants to return to their former glory they would definitely need to bring in some players and that would require funds which at the moment seems to be some of their issues but even at that I still expect them to be different atleast they have some good players, it just all boils down to the fact that a good coach with good mentality needs to handle the club.
Barcelona's biggest problem is the financial crisis, but I am sure that even though Barcelona is currently experiencing an economic crisis, Flick is confident about the La Masia graduate player, he is optimistic that he will make changes next season even if he doesn't buy new players.
The other most crucial problem in my opinion is that Barcelona lost an influential figure on the board of directors like Johan Cruyff because currently Pique cannot be relied on at all, maybe replacing him is a good thing for Barcelona to do at this time.
That way, Barcelona will once again be victorious in the hands of Hansi Flik. because he is very confident that he can win Barcelona and doesn't care about the criticism made by Xavi regarding Barcelona's economic crisis.