The current system DOES allow it

Technically true, not in practice. On almost half of the provinces (those with less than 4 seats)* you risk your vote going to waste if you don’t vote for one of the big two parties.

it’s not a system like the American one, what does not allow it’s the will of the voters

It’s the same issue, but worse in their case. The American system also allows it if only the voters massively voted for some third party.

those on the right do not like a center party.

Do they?

* In fact, you could even include those with 5 seats, which would put it over the 50% of provinces and 30% of seats.

Unfortunately the current system doesn’t allow a small center party to survive and add nuance to the political scene.

There isn’t a binary «veto»/«simple majority». Supermajorities exist, and the Council already has rules like double-majorities to preserver a smaller country’s voice. Vetoes only work for small groups, and cause gridlock in all other cases.

Ireland, for instance is constitutionally neutral

That’s why article 42 is worded that way. Ireland (and Austria) not being able to contribute directly doesn’t mean that the 25 other countries can’t act.