It would be extremely bizarre to randomly have pokemon on your team faint when you send out a pokemon. Imagine a team of 5 Shedinja and something with this ability.That is an improvement and could be fine on a Pokemon with weakish defences if it still took damage switching in, I like the do 1 damage to the team idea from a competitive angle, but don't see how it would fit flavorwise.
I don't really see why we need to weaken Entry Hazards, its not like they really break the game they just make one type of team possible (Full Stall) and help some sweepers to achieve KOs.
Focus Sash isn't that broken; I don't see why we have to go out of our way to neuter it when this ability is used. In addition to entry hazards, sandstorm and hail also act as potential counters to Focus Sash.
A team that truly desires to abuse the Focus Sash can easily incorporate spinners anyway. However, the point of making a more competitive spinner to make something that is easier to use and more ideal for this purpose - to allow its versatility to enable more viable teams. To prevent the use of spinning for a specific purpose seems a bit paranoid unless that purpose has been shown to be uncontestably broken within the game.
In my opinion, removing 1 level of each spikes is not really that bad (especially that ill-thought out stealth rock); but if you think I am biased against entry hazards, perhaps an alternative would be a pokemon (poison-type) with the ability to clear 1 layer of entry hazard by priority: Stealth Rock-first, then Spikes, then Toxic Spikes. It would also be able to rapid spin (perhaps even learn a rapid spin of an alternative type).