beam design above the joists

huangyhg

beam design above the joists
i wish to eliminate a wall separating two 20' x 18' rooms in a conventionally framed house.  the wall supports 2 x 6 x 18' timber joists which carry the ceiling drywall and ceiling fan.
to avoid falsework, and to hide the beam, i would like to add a beam in the attic above the 2 x 6's and place steel strap hangers from the beam to the 2 x 6's, then remove the wall.  i would place posts at the ends and bear on new rc pads.  does this seem feasible, or has something like this been performed before?
also, to get the beam in the attic, there are small vents open to the outside under the eaves.  i propose a built-up beam of 2 5/8" wonder board webs and 2 x 6 flanges that i would fab in the attic, with everything pre-cut and grooved.  are there obvious problems with this in regards to design and construction?
thank you for your insights, ~zeke.
zeke:
a couple of thoughts:
1.  have you looked in the attic and is the entire length above your wall clear for the new beam?  sometimes, interior walls are used to launch struts upward to support the sloped roof framing above.  the struts could be in the way of your beam if they exist.  also, your new beam would not only support the ceiling weight, but also the roof dead and live loads.
2.  if your new beam is placed "above" the 2x6 ceiling   
---also ---
i did want to say that your concept does make sense as a viable solution to your need to remove the wall.
jae,
thank you for your insights.  
1.  yes, there is a strut to the interior wall from the roof framing.  this i can temporarily remove after adding two struts from a member secured to the 2x6 ceiling joists on both sides of the strut.
2.  thanks for pointing out the unbraced length.  i will add kickers from the top flange to the 2x6's for lateral support.   
3.  i will size the beam per local and national codes.
thanks for the vote of confidence.
~ zeke