When looking for improved definitions, EONIA may be a good starting point. The EUR overnight rate EONIA is one of the few OTC fixings, that does have a definition that looks at actual trades: “Eonia® (Euro OverNight Index Average) is the effective overnight reference rate for the euro. It is computed as a weighted average of all overnight unsecured lending transactions in the interbank market, undertaken in the European Union and European Free Trade Association (EFTA) countries.”  This could serve as a template for an improved definition of LIBOR and ISDAFIX or their potential successors, but would probably still require some amendments for longer term money market rates (LIBOR). The very short term nature of EONIA helps in this case, as the credit risk in such transactions is less of an issue and there is still some unsecured lending actually happening overnight. It is not obvious, that such an amended definition alone would help a lot on 3 months tenor and longer money market rates, as there are quite simply not a lot of transactions out there. If a market is so dried up, that every little trade represents a significant share at the time, then it typically also is prone to manipulation.