He intends to take over the world. I'd say he's willing to risk something. A single (successful) experiment doesn't seem like much to me.

He indeed did it only to be able to pilot that Gundam, that's not what I meant. I meant that particular Gundam stands for more than just its capability in a fight. Even if it's symbolic, it's still the vehicle of the leader of Gjallarhorn. That's why it was worth it to risk the surgery. He wouldn't likely have risked it for some random, noname Gundam equipped with the neural interface system. Even now he did at least succeed at making those couple of geezers neutral.