A Christian funeral should not be focused on the body of the person who died. The focus is on the life that was lived. You will save money if you have the service in the church, because you shouldn't have to pay for funeral home facilities you don't use. Funeral homes may not like this because it reduces their fees, but I would stand firm. The best value is 20 gauge steel.
Hardwoods are very expensive.
When early Christians died, they did what the land would allow them to do. If the ground was soft, they dug a grave. If there were caves, they used them as a mausoleum. If the ground was hard, and there were stones, the stones were piled on top of the deceased. In the rare instance where they were crossing a sea, they were buried at sea.