The thing is, the faster your move up the schedule in Taiwan, the more pressure there is for Japan to intervene more directly in Korea, which will be unpopular with both sides.
Why? Especially if trying to colonize/keep order in Taiwan is much more than Japan bargained for in terms of tropical disease of local (especially aboriginal) resistance, and it is feeling some tooth and jaw pain and headaches as a result.
By the way, I can easily imagine the Japanese thinking better of it and *not* trying to make a takeover of Taiwan permanent in the 1870s if somebody major proposed it at the time. If they decided to give it a try, I can easily imagine them suffering for it, even if they ultimately succeed. I cannot quite see the locals of any kind truly being able to repel the Japanese on their own if the Japanese eat the cost (to save face) and persist. I can imagine the Chinese, if roused to action, possibly building up their navy, supporting Han guerrillas, and ultimately fighting and beating Japan to drive them out, but I honestly see the odds of them doing so over this territory - Taiwan, in the 70s, as less than 50-50.
Here's one go-to outcome I do expect or accept - a random western power swings by and lifts Taiwan right off Japan (and China), because it sizes up Japan and in the 1870s just judges Japan is playing above its pay-grade. I don't see it. A French-born American actually worked with the Japanese expedition of '74 and greatly encouraged it. He saw the Japanese as better, more 'civilized', more hands-on administrators than the lackadaisical Chinese, and I think all the western powers would tend to think of Japan at this moment as better keepers of order and safety for western sailors and merchants than a Chinese administration or aboriginal non-administration. Sure the Japanese faced some episodes of rebellion in this decade, but these were all briefer, less lethal, and less destructive than the rebellions the Chinese were still dealing with through 1877, like the Dungan Muslim revolt that was keeping General Tso, the chicken patronizing militarist who outranks Colonel Sanders, busy at the time.
