In camera RAW, to save a JPG you click on the 'Save image...' dialogue and another window opens with the JPG options.
To skip this window and directly save the image, you hold down the ALT key and click on the 'Save image'.
Is it possible to reverse these settings, so that if you want the JPG dialogue to open you have to hold down the ALT key and to save without the dialogue, you just click on the save button?
Nope...and it ain't gonna change. Option/Alt clicking to bring up the dlog would mean any click on the button would do something that might have unintended consequences...Option/Alt clicking to bypass a dlog is a Photoshop standard anyway so you may as well get used to it. (which is another reason it ain't gonna change).