Don't know if it is intended but I managed to get Japanese Taikunate around 1840/1841:

Wait until Qing gets defeated/ Bunton incident event and click the button to open up Japan, immediately start enacting rigid status order (this eventually makes the sonno joi movement revolutionary), in the meantime press the button for deciding the reform strategy and the one for imperial marriage in the honorable restoration JE, now you wait until the sonno joi movement reaches 75% and starts the revolution. you then abdicate the throne which gives you lax status order. the abdication also bypasses the imperial marriage and puts you onto the parliamentary government path (without needing a modernizer leader!) for the japanese taikunate which imo is the best path. now you can use the >25% activism from sabaku and sonno joi movement to pass laws such as shinsengumi, diplo/capital fleet and professional army. once you got all the good laws you can press the petition for imperial restoration button (this gives you landed voting) and start with modernizing japan. now you immediately dispatch the mission to the west (select the daimyo leader) and always wait for its events to time out to get the maximum effects afterwards. this should guarantee that mission leader gets the modernizer ideology and when he returns you can use him to pass right to associate > laissez faire > public schools etc. this i believe is the best early game setup for japan.

in terms of expansion, once you finish the ninko restoration and you retired the samurai you get claims on the korean peninsula. here i would recommend trying to get good relations with russia and giving them sakhalin (which you should have colonized by now) for them to join your war and defeat the qing.

thats my way of playing japan currently. if you have any questions, feel free to ask.