In the (likely) case that we don't sign any strikers this summer, I think Ruiz is absolutely worth bringing up for most of the preseason. And, if he shows maturity there, some CDR callups and regular training for the first team should be in order like Aleña had. Same goes for Mateu Morey. Both look to be absolutely standout and well rounded players.
It'd be a total waste to give those preseason minutes to Paco IMO, seniority be damned. That is the time to truly experiment with the team and see how things could work out moving forward, so you have to think with a long term perspective. In an ideal team you want your backups to be young players growing into the role, which is what Ruiz could do. Paco is really not useful for us now or in the future. He's on a bad contract too, and deadweight on the level of Gomes. Ruiz could genuinely be something great in the future, much more worth the investment in development/playing time.