alright, so i managed to compile mtk_uartboot for arm for use with my raspberry pi 4 (link if anyone wants it, maybe @981213 can add it to the release page for anyone else who wants to use it with a Pi 3/4)
(i was running 23.05.0 when it bricked)
used this command:
/mtk_uartboot -s /dev/ttyAMA1 -p bl2-mt7622-1ddr-ram.bin -a -f openwrt-23.05.2-mediatek-mt7622-linksys_e8450-ubi-bl31-uboot.fip
that got the router booting and i was able to flash the new installer from there
pic of the serial connection: (UART4 on the PI):
both my rt3200's are up and running now on the new layout