As Jemiba mentioned, this variable-incidence wing could well be a logical outgrowth or Richard Vogt's preference for tubular, often steel spars which often served as fuel tanks.
It's a corrollary to the variable-incidence wings used on some experimental carrier aircraft and flying boats to improve visibility and/or reduce landing gear length in the landing configuration (see, for example, http://www.secretprojects.co.uk/forum/index.php?topic=6577.0).
I don't see why that setup would necessarily limit the amount of bombs that could be carried or prevent the use of rocket projectiles, though a self-adjusting gun sight would be handy.
The obvious advantage, in this case, would be the ability to lower the nose on a bombing run to get a better view of the target. On a strafing run, the effect for fuselage-mounted guns would be the same as the downward-inclined guns used on some contemporary, especially Soviet, aircraft, in that the aircraft could maintain altitude but still bring the guns to bear.
The downside, other than increased structural weight, would be some handling quirks and definitely some loss of speed on the attack run due to the increased fuselage frontal area. Wing guns would also be problematic in the "skewed" configuration.