Unfortunately you can't add any more operators to the DX10, however you could probably add multitimbrality! Yamaha's YM2164 sound chip at the heart of the DX100

Unfortunately you can't add any more operators to the DX10, however you could probably add multitimbrality! Yamaha's YM2164 sound chip at the heart of the DX100 is pretty well understood, and very similar to the later YM2414 used in the multitimbral TX81Z.