In general, you should have the option to be relaxed about the very likely chance to be able to debrick your device if anything unforeseeable happens: mtk_uartboot should help you
The third link also leads you to the sources to build the original Uboot from GL iNet.
The openwrt Uboot artifact as an output of the build process is rather lean and comes without WebUI. So, I would prefer the original from GL iNet.
You can either ask for the download like I did or, build your own, which is always the preferred method (for me).
Regarding mtk_uartboot: The MT6000 should behave very similar to the X3000 for which I have tested the active push of the uboot successfully as it was described here.
Cheers, Frood