Chess ethics

That's like the penalty taker in football telling the goal keeper "I'm going to hit the ball soft and to your left along the ground". It completely takes away any element of surprise and gives your opponent an edge. Why discuss it when you can just play it and analyse the position together afterwards?

why would you want to do that? i mean i could say that i will play bg5 and then simply not play it.

I mean a way that one cannot go back from a promise. Simply a proposed line that can be agreed apon and instantly implemented. Thanks for the responses.

***Perhaps if a game goes sicillian and someone suggests a certain variation?

your first comment was deleted, but if you download scid there is an option to start a game from an opening vs computer. there is currently no way to do that on this website in live though