Cool dude!
Christ’s Passion is the only way to salvation, so He is the only Mediator. No saint can offer up blood to God for anyone’s salvation apart from Christ’s Passion. Through Christ’s Passion alone are we saved. “By His wounds we are healed,” as Isaiah says.
Also, I would say Jesus is the one Intercessor as well. No one’s prayers or sacrifices are heard in Heaven unless they flow from Jesus within them. So Christ speaks, prays and suffers through us, fulfilling His role as Mediator and Intercessor through and in us. Remember how on the road to Damascus, when Saul was persecuting the Church, he heard Jesus say, “Why are you persecuting me?” By persecuting Christ’s Body, the Church, Saul was persecuting Jesus because Christ and His Body are one.
When a saint prays, it is Jesus in him motivating him to pray. So Jesus is still the one Intercessor, because He and the saint are united. When a saint offers sacrifice, it is offered up in unity with Christ’s sacrifice and without the Passion of Christ, the saint’s offering would be useless. Jesus gives the saint the strength and courage to make the sacrifice, gives him the grace, and mediates through the saint. The saint does nothing without Jesus’ mediation.
Only through Christ are we saved, His Passion, His Intercession, His Mediation. However, Christ is not separate from His Body. He prays through the Church, suffers through the Church and acts all over the world through the Church. Therefore when saints in Heaven offer their intercession, they are not depriving Christ of His role as the One Intercessor or One Mediator. They are acting in unity with Him, motivated by Him, and are acting only in Him and through Him. He is everything in what they do and are. They can do nothing independent of His Mediation. Without Him we are less than nothing. Even the Virgin Mary would be nothing without His Mediation, His Passion, His Intercession, His Sacrifice and Love.