So, I want to add an alternate universe set in a timeline where the Covenant glasses Earth but multiple factions survive afterwards on planets still un-glassed. Is this idea alright?
No, since it's a full-on alternate universe. I should've halted you with Valhallaverse last time, instead of being wishy-washy. We allow one-off stories or articles to be alternate universe entries, so if it's just an idea or story you want to run with in one article, that's alright. Otherwise, however, we require you to stick to canon events.