The solution to what you need is a dedicated keylayout, useful if you extensively write in these languages, or a generic, linguist’s keybaord layout, like US Academic I created many years ago, free download, together with other keylayouts, here:
I argumented that it is better than Apple’s offer, U.S. Extended, because it does not cover all the possible combinations and also it is not mnemotechnical. You may get any combination you wish, as attached.
Nevertheless, if you wish to create a custom keylayout, with something like a with ogonek and acute accent, you should get this by copying and pasting the combination into a custom keylayout, disregarding how you wish to get that, at zero level or via option/alt key.