I don't get it. Is Portugal alone in having separate keys for accents? I have a key for ^ and a key for "o". If I type ^ and then o, I get ô. If I want to type a literal ^ i press ^ twice. Same for `,´,~,¨ (which is not ideal for programming, but I'm used to it). I'm missing the inverted ^ because it doesn't exist in Portuguese but you get the point. The only letter than has a dedicated key is ç.

Wouldn't this solve much of the problems of these keyboard layouts by reusing the same letters?

Same in most other language layouts.

But I'm talking about the euro-layout, there are keys for ý, ä, ü, ö, é, .... All of these are 'western' special characters, no eastern europe (slavic language letters) or greek letters. So users of _these_ languages, need to use dead keys or some other method (I don't know to get greek letters with this layout) for at least some of their 'special' glyphs that are not, by chance, also used in another language (for slovak and czech that's for example ä, ú, á, é, ý and í).

https://eurkey.steffen.bruentjen.eu/pics/layout.png

It does in fact include the polish Ł, czech ř, slovak ô, check the Layout page and the shift and Altgr tabs, they are made using the diacritic dead keys