If a block from a configurable list is within range, it should always show up directly after the player tab, and optionally only show one instance of that block.

There should be an option to make crafting tables and ender chests should always show up as the first 2 tabs (when available), and not show any duplicates because there is no reason to switch between two crafting tables/ender chests.

The no duplicates for Crafting Tables and Ender Chests has been implemented in version 0.8.0 (alongside Anvils, Cartography Tables, Grindstones, Looms, and Stonecutters)

I like the idea of an ordered tab list, I'll look into implementing that feature sometime in the future.