I. Think it would be more fun if someone else were to to play the master. That said i can also make my own if not an option. When it comes to Rider, a female companion would be optimal and preferred for her, but a male one is also viable. Ricardo in particular does not match the criteria personality wise however. Someone like 4th war Waver who's not confident to take the lead or who can be flexible and willing to break rules (and give praise) like Kairi from apocrypha war would be best.

Although... Ricardo's goals could share some affinity with Rider, so if there is not a more compatible servant out there for him, Rider could take the mantle.