Increase binary datatype limitation from 255 bytes to 65536 bytes

In a project I'm working on, binary string 'varbinary' used as fixed array. Array elements change by INSERT(str,pos,len,newstr) function. Varbinary fields filled at insert with 0x00 (the zero byte) by setting DEFAULT option to '\0\0\0 ... \0'. The problem is that in my company use such programs, as Naviсat, which clears default '\0\0\0 ... \0' value at any table edit. Alternative - use datatype 'binary', that filled with 0x00 (the zero byte) by default. But its limited by 255 bytes only, error: "1074 - Column length too big for column 'row_array' (max = 255)". It will be great if limit of binary datatype increases to 65536 bytes or more.