Goodell dug a hole for himself so deep he can't get out. If he lets an independent arbitrator take on the appeal, the Wells report will be shred and revealed the sham it is. If he refuses and makes himself the arbitrator, the NFLPA sues and goes to court where the Wells report gets torn to shreds and revealed the sham it is.
Millions upon millions were spent for this Wells "investigation". Goodell in a no win situation. Goodell brought it upon himself. To court Brady goes and to the unemployment line Goodell goes.