I voted for & I am stoked to see such a high level of engagement. 
Adding 200K worth of ETH to the treasury to me is a stepping stone to setting up a 80/20 INDEX/ETH pool for the treasury at a later date. For this reason alone, it make sense to purchase the ETH in the lead up to deploying this pool.
INDEX liquidity is definitely something to be considered and i think that is well addressed in the post.
However, reading over the comments. I do think more needs to be done to communicate a roadmap of sorts around this topic. It might need a call or two, to handle all the questions. There will be questions about entirely different strategies and they would fall outside the scope of any roadmap article. Communicating a vision stitching everything together will help concentrate the discussion. It is a broad topic and great to see @DarkForestCapital taking on this mammoth task.
I posted this proposal, here, to see what people think about the idea of token holders and contributors buying INDEX from the Index Coop Treasury.