I'd build my own version of Wiring board, same as original but changed from FT232BM to FT232RL.
after burn the bootloader .hex file (from Barragán) into ATMega128 and config fuse the right value.. when I upload sketch on Wiring, but ony wierd result is
Atmel AVR ATmega128 is found.
Uploading: flash
Firmware Version: 1.15
Firmware Version: 1.15
Programmer is not responding.
and nothing programmed into board, then I try using the other stk500V2 compatible bootloader. it's working well on AVRStudio 4 with stable result connect / reconnect / verify , that's proved my board is ok.
and double check to use commandline software "avrdude" that's work fine too..
then this solution may be solve problem on Wiring too.. but Wiring using uisp utility and not support to stk500V2 protocol..
can Wiring software modified on upload utility from uisp to avrdude or not?
if interest, I can publish stk500v2 bootloader code to the forum