How about just gypsophilia with some dramatic foliage thrown in. E.g, banana plant leaves. ( will get them now in B&G and other garden centres quite cheap, I got mine 50p each last yr). You can keep them as house plant, trim all overlarge leaves and use as you please.. Or you could use whole pots of them in the church, and add other plants. You have a chance in the church to use living and cut flowers. Where many people would use a cut flower, you could use a living plant, and get it back again to plant.Just decorate or hide the pot.
I have seen some fantastic arrangements of cauliflower, broccoli and cabbage in very prestigious places. They were picked quite small with as long a stem as poss, and looked fantastic. I have even seen carrot foliage used as a backdrop.
For the Church,you want thing to look great. But remember that most people are looking at the Bride, and not noticing the flowers. Flowers will be more noticeable at the 'do', after. Here is where you put sweet peas, etc. For scent and colour.
Late now, going away to think more, and to bed! May have more ideas tomorrow. No, Tues, as my son's B'day Mon so cakes to bake, etc.