I believe riot games has done something similar to this, but to a far greater extent. They forced people to utilize their launcher and made sure to OSRS gold check if hashes don't match. If it found it does not, it is going to upgrade the match for you .
However, for coffee, it is much harder because bytecode is easier to modify compared to classic x86 architecture.If enough resources and money had been placed together, they can earn a c++ loader, which can minimize the matter greatly. Afterward, they can add real anti cheat which can actually have a bigger impact than the present.
It won't stop botting entirely, but it will add a huge cost to creating a farm. Since bypassing said anti cheat requires some time, so public clients will cost a good deal of money.
If you go into Runelite.net, they have listed how many men and women are about the Runelite client at that given moment. You can compare this to the Cheap Rs gold official player counter at different times of the day. Pretty sure OSB has some counter tops too.
The new customer should support open source modules, the neighborhood will gradually port them to C++. Jagex host their own hub similar to runelite's'plugin hub', they approve new plugins upgrades akin to the runelite team's current workflow.
Instead Jagex may get more concerned with runelite and choose a Microsoft style solution to open source development.