I'll start off saying that there is no separate page for the alert levels. Currently, the best definition for them is on the Captain page, but we're actively working on making a separate page for the alert levels. You assumptions on alert level progression is generally correct, however as Greenjoe said, this is sometimes not possible with the manifest, although whether a someone going missing constitutes blue alert is dependent on the command team.
As for my opinion on the matter, I've never found suit sensors (or suit sensor location) a major issue when it comes to antag play. Granted, I don't often play antag, and haven't recently. I do know that there are ways to subvert suit sensors. They're, in my mind, a logical tool that medical should have access to given the nature of the environment our characters are in. Space is dangerous. Ships are dangerous. I would much rather expand or buff an antag's tools to subvert suit sensors, like a jammer, than remove them. In my frank opinion, keeping them code locked or removing them outright harms the entire gameplay loop for First Responders (Note, that is my main role so I am biased in that capacity) outside of the very visible mercs, burglars, etc.
TLDR; Give antags tools to subvert, don't remove the useful tool.
TLDR of the TLDR; Put a door in the wall, don't teardown the wall itself.