I recreated it and do provide the source file so you can patch from ASM or do more changes.
I provide a IPS too. The characters rotate but the preview shows the wrong companion. Sure this could be done more clean but it works and you can play as what character you like any time.
(Deleted since there is a release)
Database match: Tiny Toon Adventures (USA)
Database: No-Intro: Nintendo Entertainment System (v. 20180803-121122)
File SHA-1: 110796622E50C2E8C20B1430ACADC5BAE5F36586
File CRC32: B34ED396
ROM SHA-1: 3C011E4EA5EB7E93299347F8009E5BDF51E223EB
ROM CRC32: 99DDDB04