Chi-Nu is better as an analogue to the Sherman. Let it be BR 3 instead of 4. It has max armor of 50mm and poor anti-infantry capabilities. Cannon is nice but can be deflected by angling by BR 2/3 tanks. If it helps in comparison, both early sherman and chi-nu are 3.3 in WT (M4A2 is 3.7).
Ho-Ni III is just a Ho-Ni I with enclosed casemate. Let it be BR 2 instead of 3. 25mm armor and no MG. Cannon is nice for AT, but it is completely vulnerable to early AT rifles. Still an inferior option to the M3 Grant/Lee. Btw right now you can only peak out as commander in the enclosed casemate, which makes no sense, but that’s another issue.
You still have a tank in BR 3 and 4; chi-ha short and na-to, so no worries about an empty BR tier.