Agreed. I've been really wanting this as well. Please, make it so.

For example, let's say you crafted a rope tension spring, which cost you good wood, and very valuable rope, but you have no use for it other than unlocking the next research. So, it would be cool if you could disassemble it to get at least some of the rope and timber back.

This is how it worked before 0.7: you could deconstruct most (all) blocks with your hammer to get the components back. Now, only large grid blocks can be deconstructed so that you regain their components defined in their block definition, i.e.:

  <Definition xsi:type="MyObjectBuilder_BuildableBlockDefinition">
    <Id Type="Block" Subtype="TransmissionWood" />
    [...]
    <Components>
      <Component Tag="ScrapWood" Count="1" />
      <Component Type="Block" Subtype="Timber10" Count="4" />
      <Component Type="Block" Subtype="TimberRound10" Count="1" />
      <Component Type="InventoryItem" Subtype="JarClayWithLinseedOil" Count="1">
        <ReturnedItem Type="InventoryItem" Subtype="JarClay" />
      </Component>
    </Components>
    [...]
  </Definition>

It looks like the components for all the small grid blocks have been changed in a way they only return the block itself:

xml
  <Definition xsi:type="MyObjectBuilder_BuildableBlockDefinition">
    <Id Type="Block" Subtype="Smithy" />
    [...]
    <Components>
      <Component Type="Block" Subtype="Smithy" Count="1" />
    </Components>
    [...]
  </Definition>

This must have been a decision by the game designers, which I can't really understand. I agree with the OP that small grid blocks should return their components upon deconstructing them where it makes sense or return different items than were put in eventually (see mechanical transmission block above). For instance, the crafting table needs wooden logs to craft, but it looks like the logs were cut into proper timbers. If you deconstruct it again, it shouldn't return logs again, but timbers or scrap wood for example.