Sink thing lasts for a day. Sink items won't be announced and will be unknown, only way to understand is to carefully follow trades on the same day. Lucky people who did manage to inventory on things before their cost increases will manage to make money on the extended tern, but it wont change the fact that fresh money making approaches will become viable again as the prices will nonetheless increase. Deeper systems could be put into place, for example the entire process could detect individuals who hoarded millions of the same resource beforehand and prevent them from selling the Sink thing in precisely the exact same day, I am pretty sure Jagex could develop something similar to this.
My only other thing is what's the point of making these already worthless items have value? For the sake of getting value? They're worthless for a reason. It is like making it expensive and taking any other low cost object or rice, for what stage? Since the two things are not intended to be paired together other than someone is making money off of the price gouge, it wouldn't flow with the rest of the economy. It is simple economics bruh. And the detection process is only a band-aid on a notion lol that is bleeding. What is the purpose?
The majority of those things are only"worthless" due to bottling or massive resource influx from terrible boss drop tables. They used to be worthless back in 07 or for quite a long time in OSRS. Also, RuneScape has zero item sinks due to fatalities being 100% secure for years now. Items not being sunk will eliminate significance as new ones come into RuneScape far faster than they are needed by new players. Doesn't mean it's not happening because it's occurring slow for high value items. It's not like that is suggesting we artificially create bamboo longbow(un ) 10k for your day.
Making skilling for money worthwhile again, there's absolutely no profit in Selling smelted swords, combined potions, and created Armour, and very little gain from collecting skills, should you cut the quantities of stuff in the current market, these things will become more valuable again. Imagine players that are low smithing steel scimitars and selling them for profit, this can actually occur.