Sounds like a good plan.
There are a few studies out there that have shown that mycorrhizae induce resistance to Early Blight in Tomato plants. I'll vouch for that, I've had a dramatic reduction in Early Blight infections since I've been inoculating my seedlings the last three years. Unfortunately it doesn't work for Septoria that way.
Last year was really bad for Septoria, it showed up earlier than usual and very aggressive. In the previous few years I had very good results at control with just teas and Actinovate. This year I'm going to be more aggressive myself and alternate with a copper soap fungicide, Actinovate, Compost and Vermicompost Teas.