Idea for a new Steam service

It's already there. It's called "Steam Sales" or "Family Share". Restrictions apply.

no, as often as they have sales you still are better off just getting stuff then. in the longrun the sub would prb be more than getting games on sale. i also hate the idea of losing access to things when service is expired. this mmight also require online authentication for all games as to check if your sub is still valid

No. They have good enough sales anyway.

That's like buying random game. Why not just use the money for games you actually want?

By the time you've spent X amount of money on subscribing to this service, you may as well have spent it on getting games you want whilst they're on sale. Since we already have tons of sales, I do not see the need for subscribing to get games.

Why? Subscriptions are a leech and punish you for not playing as obsessively as possible.