I'm going to look like an -blam!- in saying this, but whatever. If a solo flawless run is taking you 4+ hours, then you have big improvements to make. Even playing conservatively, it shouldn't be taking more than 2. Maybe it's your strategy, or your loadout, or execution of damage phases, there will definitely be stuff you can change. The faster you beat it, the less likely you are to have more disability-induced interruptions. That said, the requirement to not leave is there so players can't Alt + F4 or equivalent when they're about to die and resume with less progress lost than if they had to restart entirely. Kicking for inactivity is also reasonable - sorry, but the game can't know the reason why someone is inactive; I'm almost certain the timer is more lenient when solo, though. A typical person can easily go for a bathroom break mid-activity without being kicked. To remove these things benefits you and others in your situation, at the cost of the integrity of the achievement for everyone else. I have sympathy for you and your experiences, but I can fully understand why Bungie have in place the systems that they do, here, and I don't see situations like yours being enough to make them change.

Yeah. Been asking for this for years. Doubt Bungie gives a crap about what their players want anymore. Anyways, here’s hoping😬