Scheduled sex is itself fine, however most men (at least those worth considering as a long term partner in the first place) derive much, if not most-all, of their enjoyment of sex of the human connection, and feeling the desire, arousal and pleasure of their partner.
Sex with someone who isn’t enjoying it, and just passively accepting does not sound appealing at all to me, and I’d be weary around men who are open accepting such an arrangement, because imo it strays into areas of ambiguous consent.
At that point, it’s probably similarly enjoyable, and much healthier, if your partner takes of their urges by masturbating. You could potentially even support a future partner in that, by e.g. gifting him solo male sex toys like fleshlights. It shows that you genuinely care about his pleasure, even if you’re not into actively participating in sex. This is for example a relationship I (as a cis man) could exist in perfectly happily.
And whilst it’s obviously not for everyone, and it can be emotionally challenging, and requires a high degree of emotional maturity and communication, I would also at least consider the potential for an open relationship, where your partners urges could be satisfied without your participation.
Also, even if you do decide to try it with a partner who wants to try your scheduled sex idea, I would definitely not start with sex.
Start slowly, by for example offering to jerk him off, or allowing him to masturbate to your naked body. Try it out slowly, and then see if you’re both comfortable with this type/level of intimacy, before jumping straight to penetrative sex.
It’s a very delicate affair, not just for you, but for the man as well. Having sex with a woman who is unresponsive, and just passively accepting, has a potential to make your partner subconsciously feel like they’re abusing, or even raping, you (even if you explicitly give consent, the subconscious is rarely swayed by rational arguments), which has the potential to lead to serious sexual trauma.