Currently Barcelona does not have many solutions even releasing several important players didn't help much because it will impact their performance, as you said building an internal squad might be a good solution, but it takes a long process and time. It's not easy to make a decision in this situation and must find the best solution in the near future, If Barcelona can win the Champions League, maybe that will help a little it's just that it's not easy because there are many competitors there.
Strategies in Barcelona last decade are bad and ridiculous. They generously provide their players with very good salary and long term contracts, then when their players perform bad, less than their club's expectation, they struggled to sell those players or even failed to let those players out in loan transfers. Other clubs are not ready to cover all high salary of Barcelona players or share main of high salary. Barcelona consequently had to spend big money for player salary while they did not get contribution and benefit from those unused players.
This problem in strategy has not been changed in a better way in Barcelona and it continues to affect their financial status. Playing in Champions League quarter finals will help Barcelona in finance a little bit but they can not bet their club's financial health on Champions League. Restructure their player resource, budget for salary each season are important things they must do as soon as possible.