Best plants for over a septic field?

I'm about to leave the gardens I've been working on for the past 14 years and move to a larger blank slate property in 6b. ( this is hard, but exciting)

While I've lived on septic in the past, it was before I was serious about the permaculture gardening. The septic bed is in a premium, full sun, southfacing spot. I know I can't do trees, shrubs or raised beds on it but I don't want to leave it as lawn.

I have found that having a good range of perennial flowers, that cycle so something is always in bloom, has let me host a wide and healthy range of pollinators. I'm leaning towards using the septic field as the main flower area. Are there likely to be any issues with this plan? Any things that would be especially suitable for this kind of space? Would roses or lavender be fine?

The main plants I have or can easily get are: roses, peony, lavender, yarrow, hardy geranium, poppy, iris, day lily, milkweed, liatris, sage, Russian sage, sedum and spiderwort.

I have considered growing grain for chickens on a septic as well. Interested to see some better informed answers though!

Think shallow, shallow roots. If it reaches deeper than white clover and grass, it's a recipe for trouble.

Messing with a septic field is a very expensive gamble, on the order of $20K to play.

I like to corn over my septic field.

I'm thinking of raspberries over my neighbour's leachfield which is on our property - it has shallow roots but likes it damp and shady though.