He, he cool idea (pun intended)
That's the same size handle shaft as on the Wico's isn't it?
You use a compressor to get the air to move through the tube or does the motion of the stick somehow create airflow?
to answer your first question im uncertain what similarities if any the happ and Wico's share. i would imagine most sticks are nearly identical and any differences are likely just cosmetic,though I might have to pick one up for comparison.that is unless someone here has an old wico thats passed its usefull life that they wouldnt mind parting with to broaden this projects scope. 
Sorry, I should have checked myself. I just bought a set of Happs 360 metal SlikStik handles to go in my Wico bases. I just wasn't sure if it was the 360 model, but indeed it is. In fact the handles are very particular per type of joystick. Though, apparently Wico used the same handle on several of their sticks. The 360 which was originally a Wico product.
Are you gonna sell this type of joystick handle or just a plan on how to build them? I can imagine getting the shaft machined, but where would one get a bat grip like that? Or is the plan to drill a hole through the shaft and puncture the grip with a lot of holes?
sorry for the late response, i have not internet access at home at the moment and i can only log in at work..
contrary to what i had initially hoped, this item would have to be an assembly. i had thought that perhaps I could do this in one piece and in turn modify an existing joystick, but what im finding is that is that its much simpler to make it out of two pieces from scratch. modifiying an existing stick IS possible but would require some unpleasant parting lines in the conical handle. which imho is not acceptable

The conical handle would start off as a piece of round stock.it would then be turned on a lathe having the internal diameters drilled, bored and finished. it would then go to mill having a series of 10 flats about twice the diameter of the drill bit placed on its diameter over the lenght of the part. this will give the drill a nice starting point without walking. it would then be drilled and returned to the lathe department to put the profile on it. then that top section would be mated and permanently bonded with the much simpler lower shaft section.
all in all alot of work for something so really insignifigant, and most likely not cheap.. but its totally for fun! once i build the protoype and get a handle on the total machining time ill have a better idea of what this little gem will cost.
depending on if i could do it without loosing my shirt i would offer the service through the machine shop i work at, but most likely i would simply provied the blueprints and bill of materials here for anyone to have done themselves.
ive taken enough from the emulation scene.. i cant code in C or crack hardware protection so im useless there. but I do good cad/cam work

.. and I would like to be able to give something back to the community which has given me so much joy..
this and a couple of other ideas i have in the works which i will be posting here soon are my chance to do that.