I was reading that Cardiff are represented by the FA of Wales even though they play in the English league system, yet Cardiff, along with Swansea, Wrexham, Newport County, Merthyr Tydfil, and Colwyn Bay are not allowed to enter the Welsh Cup (which would grant them a UEFA Cup spot if they won) because of their English league participation, so these teams are effectively squeezed out of Europe.
My understanding though is that it is ultimately up to the national associations to submit their entrants for European competition, so could either the English or Welsh FA make a place for Cardiff were they to win the cup (or come runners-up and have Pompey finish 6th)? It would probably have to be at the place of a team that a) would qualify via the Welsh Cup b) would qualify for UEFA competition due to league placement in the EPL, and I can't see many people buying that.
Still, it seems silly due to the bureaucracy of it all, but if Cardiff win the FA Cup then they should be in the UEFA Cup.
On a side note, Cardiff have actually won the FA Cup before, but it was in 1927, before European competition and thus there is no precedent I can think of.
This is different ghostworld, Monaco do not have a national team and FC Vaduz will never qualify for Europe.
More to the point, Monaco do not even have a national association, at least one recognized by FIFA. FC Vaduz actually always qualify for Europe, but as representatives of Liechtenstein because they always win the Liechtenstein Cup, which gives them a UEFA Cup place. But through the Swiss leagues, I suppose its a long shot.