[ONE Android Development] LiquidSolstice:
This is awesome that you're providing this guide and all, but there's a few things not quite correct/could be simplified.

It is impossible for you to wipe TWRP from TWRP. Even if you manually format every partition in the TWRP menu, you won't get rid of TWRP. From what it sounds like, you already had TWRP, why would you flash TWRP again?

You don't need any toolkits to use ADB. Which leads me to my next point...

You don't need to use ADB sideload, at least, not in your specific situation. Recent versions of TWRP offer full MTP support, you just need to enable it in the "Mount" menu, and it will show up on your computer in the same way it does when booted into Android, so you can copy your zips back to your storage.

In your case, you didn't need to flash the firmware over again. Firmware is a one-and-done deal (and you can't "erase" firmware from recovery). Except official CM nightly builds, ROMs usually do not include firmware bits inside them. Clarify with your ROM dev to make sure.

You don't need to unlock your bootloader again. If you already were running a custom ROM, your bootloader is already unlocked. Running the unlock command a second time is useless.

What most likely did happen was that you're used to copying your ROM zip to your phone from within your current ROM (plugging in to your computer). What you then probably did was put a check-mark in each box in the Wipe menu, and then you realized you had no data on your phone and no zips to flash, and then when you tried to boot, you couldn't because you had nothing to boot into. People new to custom ROMs panic and think this is a "brick" (not saying you think that), or they just panic and freak out that their phone is not booting. Your phone is literally only doing what you told it to do, which was wipe all of its bootable partitions and then try to boot from the now-blank ones.

Lesson 1: If you're going to manually wipe partitions through the Advanced Wipe section, Only wipe Dalvik Cache, System, Data, and Cache. NEVER wipe "Internal Storage". Internal Storage is all of your storage .When you only wipe Data, it specifically wipes everything except your internal storage (which is tells you as it does this). If you wipe Internal Storage, you won't have any on-device zips to flash (and you will lose all of your data, pictures, files, etc).

Wiping System is completely fine (since most ROMs manually wipe the /system partition when they flash, even if you dirty flash). I myself always manually format Dalvik, System, Data, and Cache before each clean flash. Why is this the case? Because all your customizations, all your settings, all your apps, basically anything you do inside Android that didn't come with your ROM out of the box, all of that is stored on /data.

Lesson 2: Don't forget that TWRP has full MTP support. Plug your phone in while in recovery, go to the Mount menu, and hit "Enable MTP". Your storage will show up in the explorer window just like it would if you booted into Android. There is no need to futz around with adb sideload.

Lesson 3: You don't need to flash the firmware each time you flash the ROM. Especially with Temasek.

Lesson 4: This is the most important lesson. Do. Not. Panic. It is ridiculously difficult to irreversibly "brick" Android smartphones these days. While you did the best you could with whatever advice you received, what you did was probably massively overkill, and is the result of some incorrect assumptions.

Take it easy. Stop and think about what you're doing it before you do it. Every single one of us who's been here long enough has done what you've done. To put it humorously, in the context of your situation, you are not a special snowflake ;). Everyone has done what you did, and they've done it at least once if not more than that with some Android phone or another.

If you've got questions or need clarification, let me know, I don't mind helping you out.