Waiting for Felix to have another good season would not be wise. His price would go insane and he would be even more coveted by all the mayor players. I agree, his acquisition is depended on Coutinho status, which should be clear until the end of the season.
No need to wait another year for him to wake up, since Valverde is staying. If he stays in current form, then he should be sold and that money (+other sells) could be invested in to Felix+DL+ LB backup. I kind of like this scenario, because we would finish rebuilding all lines with awesome talent, while being financially responsible.
Maxi for 25mil is a no brainer in any case. In this scenario he can be FW backup and Felix can be LW backup.