Disabling GPU kernel modules on startup?

[Telvee32]

I'm on the cusp of FINALLY having a working Mint installation on my Optimus laptop, having had my functioning Fedora installation ruined by a screen repair (somehow).
I have a script that disables the nouveau module, loads i915 and bbswitch and uses bbswitch to turn off the NVIDIA GPU. Essentially, the same setup that I had in Fedora. This script works when called manually from the terminal. However, the systemd service that I created in Fedora to run this script on startup just causes Mint to hang just before the login screen. Interestingly, Fedora would also hang if I logged in with Xorg instead of Wayland.

Installation steps (adapted from this guide):
1) Add these kernel parameters to Live USB

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idle=nomwait nouveau.blacklist=1 nomodeset

2) Install as normal
3) Boot Mint 18.3 MATE (or Cinnamon) with the same parameters
4) Install all updates (including 4.13 kernel)
5) Reboot with same kernel parameters
6) Clone https://github.com/Bumblebee-Project/bbswitch
7) Enter directory and run

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make -f Makefile.dkms

8 ) Add these kernel parameters to /boot/grub/grub.cfg and reboot

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idle=nomwait nouveau.modeset=0

9) Create file /usr/local/bin/Switcher.sh and set perms to 755 (removed sudos from original as original uses autostart and passwordless sudo, which I disagree with)

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#!/bin/bash

/sbin/modprobe bbswitch
/sbin/rmmod nouveau
/sbin/modprobe i915
tee /proc/acpi/bbswitch <<< OFF

10) Create file /etc/systemd/system/nvidia-disable.service

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[Unit]
Description=NVIDIA disable

[Service]
Type=oneshot
ExecStart=/usr/local/bin/Switcher.sh

[Install]
WantedBy=multi-user.target

At this point, executing the Switcher.sh file with root permissions works fine. However, if I enable the nvidia-disable service and reboot, the machine will hang just before login. This same systemd service works fine in Fedora. Evidently I'm missing something here.

Honestly, I'd much rather use Mint than Fedora as the latter tended to be a bit of a pain in the neck more often than not, whereas Mint being based on Ubuntu has tended to be much smoother for me.