That might work, assuming OP keeps a clean backup. OP is asking how f*cked would he be, if he went down the GW-A9LH path, and his Red Card crapped out.I'm not 100% certain but couldn't you just restore a pre-A9LH NAND through the GW menu?
He also likes taking it in and out, so he'd be even more f*cked, as he would need the Red Card always just to boot the damn thing.
No. Aurora Wright's v2 A9LH fork, which the guide uses, will not work with GW's A9LH.bin, unless you use BootCTR9 as your bootmanager. It won't boot up through Luma3DS' chainloader.I have 0 knowledge of how (crappy) GateWay works and all that so if I'm wrong here then sorry but anyway, v2 a9lh can also be downloaded through aurora wright's repo or just check plailects guide on upgrading a9lh for the full package. Do mind that this guide assumes CFW from SD users, not GateWay users. https://github.com/Plailect/Guide/wiki/Updating-arm9loaderhax
You either compile a compatible v2 A9LH fork, or you use BootCTR9, or you downgrade to v1 A9LH. Or you wait for GW to release an updated A9LH.bin that will work with Aurora Wright's A9LH fork.