Of course you can pray/ask for intercession from Old Testament saints. God Himself tells friends of Job to ask Job for prayers as He would not listen to Job's friends. Sometimes it is more prudent to ask someone more worthy than us for for the mediation.
And another Biblical evidence that Old Testament saints are alive is when Moses and Elias talked with Christ in the presence of Apostles (Luke 9, 31-33)
Wow, in California you could start a whole new cult with an idea like that. As long as there are people who believe you cannot approach your creator directly, anything will sell. They might even withhold communion from some THEY don't feel are worthy.
A few centuries of that sort of tyrrany and some reformer from inside the cult would have to come along and point out that God says no such thing. Those rules are man-made. (Follow the power, and follow the money.)