1 - All-acrylic enclosures can be made, at least for relatively small drivers. Acrylic has a higher initial cost than MDF, birch plywood or other common speaker building materials, but there are no finishing expenses, i.e.veneer.
2 - An enclosure with no batting does not necessarily sound harsh. The jury is still out on this, as I need to try a higher performance amplifier, and do some A-B testing against a reasonable standard.