What do you think of a 6 unit bridge from 10-15 with abutments at 10, 11, and 15?

If you are just buying time (as in 6 months) this might be "ok".  Not a cheap short term solution, but it is your money.  A much better option would be implants at 12 and 14 and a 3 tooth bridge that involves no teeth at all.

 In my opinion, a dental bridge spanning six teeth involving the teeth that you are discussing is not a wise choice of treatment.  Tooth number ten typically is a tooth with a very small root.  This is too much force for this tooth to endure over a long period of time.  I would consider the option of dental implants for the missing teeth.  This has become the standard of care for missing teeth and will keep the stress off of the abutment teeth.  Dental implants are a much better option long term.

It can be done, what you are describing is what is called "a long span bridge."  But the bridge will not likely have a long term prognosis.  Also, the lateral incisor, #10, is the smallest and weakest of all the upper teeth, and not the best tooth to anchor as an abutment (tooth supporting a bridge).  Since your are missing three teeth in the gap, and #14 will replace the larges of all the upper teeth with the strongest root structure, you should also consider implant treatment.  This way you would not have to drill #10 and #11 for the bridge.  Have an implant bridge with two implants, one in the area of #12 and the other implant area #14.  However, because the maxillary sinus is in that bone area, you might need to have an additional procedure called a sinus lift and/or bone graft, to have enough bone to place the two implants.  Either can be done (implant bridge or long span bridge), but clearly I feel that the implant approach would be the best and longest lasting, albeit more costly dentistry.