I talked to Senior Game Balance Designer Jason Attard about mods that are bound to slots and our plans for them. Here are some comments he had about the system and its future:
Many (but not all) of our current endgame Armorings, in both PvP and PvE, are bound to specific slots. This is because some less expensive items, like gloves and boots, are much easier to acquire than "expensive" items like a Chestpiece or Helmet. We've seen that instead of acquiring an entire set of gear players would often purchase the "cheap" slots multiple times and simply move the mods over into the "expensive" items, allowing players to acquire their gear much more quickly than intended. Now that most of our offhand items have mod slots we are seeing a similar pattern occur with main hand and offhand items.
We plan to make these slot restrictions more consistent in the future, with any Armoring, Hilt, or Barrel you extract from an item becoming bound to the equipment slot you extracted it from. We do not intend to add the same slot restrictions to Modifications or Enhancements, as those item mods have a smaller impact on the overall power of the item.
What he's not taking into consideration is the war hero offhand is tied with mainhand for the most expensive item piece to purchase. I'm not suggesting to set it up where everyone is farming cheap boots for their guts to place inside of their chestpeice to avoid cost. I'm actually suggesting doing something quite the opposite - buying the most expensive armor peice to modify cheaper items that don't have the desired armorings available for them.
For example, If I want a war hero armoring without a set effect bound to it - what do I do?
With the offhands the way they were previously - they didn't have a set effect and weren't bound to slot so I could do this at a steeper cost than I would with traditional gearing methods, something I'm fine with. Another suggestion would be to add pvp set that doesn't have set bonus bound to it's armorings and then we could purchase the individual gear pieces for their bound to slot armorings. Currently the only way to do this is with lower tier battlemaster armorings.
PvE players can currently do this because black hole armorings don't carry set effects, so they're free to chose between all the PvE and PvP set effects. PvP'rs are limited to PvP set effects or using lower tier armorings to achieve alternate set effects. They also are able to obtain armorings from loot tables that aren't bound to slot or carry a set effect.