Just did this by overwriting marios model pointers in the dol with the data we have from robo mario and it seems to work fairly well. this is basically a special nintendont file with a massive hardcoded patch in the file TRI.c where the other gp2 patches are located. now for you to try I did write down its essence into a big gecko cheat code you can use without modifying nintendont! Here is the .gct file you can use directly:
https://www.mediafire.com/?id3rd6udyiv7pcg
and here is the original cheat as text for it:
Play as Robo Mario [FIX94]
043FE5E4 802EA664
043FE618 802EA688
043FE64C 802EA6A8
043FE6B4 802EA6C8
04400AD8 80318360
04400ADC 80318370
04400AE0 80318384
04400CAC 802EA400
04400CB0 802EA418
04400CB4 802EA418
04400CC0 802EA434
04400CC4 802EA44C
04400CC8 802EA468
04400CD4 802EA488
04400CD8 802EA4A0
04400CDC 802EA4C0
04400CE8 802EA4E0
04400CEC 802EA4F8
04400CF0 802EA518
04400D08 802EA538
04400D0C 802EA554
04400D10 802EA568
04400D1C 802EA584
04400D20 802EA5A4
04400D24 802EA5C0
044016A4 802EA5E0
044016A8 802EA5F8
044016AC 802EA610
https://www.mediafire.com/?id3rd6udyiv7pcg
and here is the original cheat as text for it:
Play as Robo Mario [FIX94]
043FE5E4 802EA664
043FE618 802EA688
043FE64C 802EA6A8
043FE6B4 802EA6C8
04400AD8 80318360
04400ADC 80318370
04400AE0 80318384
04400CAC 802EA400
04400CB0 802EA418
04400CB4 802EA418
04400CC0 802EA434
04400CC4 802EA44C
04400CC8 802EA468
04400CD4 802EA488
04400CD8 802EA4A0
04400CDC 802EA4C0
04400CE8 802EA4E0
04400CEC 802EA4F8
04400CF0 802EA518
04400D08 802EA538
04400D0C 802EA554
04400D10 802EA568
04400D1C 802EA584
04400D20 802EA5A4
04400D24 802EA5C0
044016A4 802EA5E0
044016A8 802EA5F8
044016AC 802EA610