Suppose I had an acid HA, and it reaches equilibrium in water. Then I remove the hydronium ions. I don't know how I would do this, maybe adding some hydroxide ions. My question is can I do this and will I be able to eventually create a 50/50 mixture of acid and conjugate base? Is this a very good buffer?
You can't just remove hydronium ions because the solution needs to remain electrically neutral.
You can't just add hydroxide ions, but you could add sodium hydroxide until the HA/A- ratio was 50/50.
Is this a very good buffer?
It is the optimum ratio of HA and A- for buffering.