The "Ethiopian birr model" 

You suggested to use this model in some cases. In my opinion, it is okay to include a territory in the current part succession box that has some autonomous rights (especially the right to have its own currency, like pre-2006 Montenegro or present-day Kosovo). Therefore, in the case of Ethiopian birr, it makes sense to speak about currency of Eritrea between 1952-1960 and between 1993-1997. between 1960-1993, only Ethiopian administration existed, Eritrea had neither sovereignty nor any sort of autonomous rights. (Saying in 1978 that the currency of Eritrea is the birr is like saying in 2006 that the currency of East Germany is the euro.) The same case of Austria between 1938-1945. Even Ukraine and Belarus represents the same situation during their Soviet Union "membership", however, both countries had more or less autonomy and were members of the UN since 1945. 

I have the fear that the innumerable border modifications in Europe during the XXth century will make huge and complicated succession boxes. For example, after WWII, Slovakia got back not only its Southern territories (Which the 1st Vienna Award awarded to Hungary in 1938), but three villages near to Pozsony / Bratislava (Horvátjárfalu / Jarovce, Oroszvár / Rusovce, Dunacsúny / Cunovo) were awarded to Slovakia (Treaty of Paris) due to strategic considerations. One could say that who cares with three villages, but this territory was part of Hungary between the two world wars - and it is not much smaller than Muraköz (Medimurje)...

So I don't think each territorial change must be mentioned in the succession box. Only mention if the currency of a new country / state / autonomous province etc. (so a state-like subject that has the right to circulate its own currency) appears without precedessor (like Eritrean nakfa after split from Ethiopia in 1993, but unlike Ethiopian birr after split of Eritrea) or disappears without successor (like East German mark after the reunificaton of Germany in 1990, but unlike West-German mark after the reunification).

For example, German mark or deutschmark was the currency of the Federal Republic of Germany between 1948-2001. It would express that East Germany was simply integrated into West-Germany (contrary to the widely used "reunification" term), at least from the point of view of the circulating currency. It would also express that Germany is not the successor state of West Germany but the same country with an enlarged territory. 

In the case of the pengő, I would simply say that it was the currency of Hungary between 1 Jan 1927 and 31 Jul 1946. Northern Transylvania, Southern Slovakia and Bácska was totally incorporated into the Hungarian administration. Subcarpathia enjoyed some autonomy, but it was very little and cannot be compared to the rights of then-Yugoslav federal states, present day US states or German federal states.

Naturally, this is only my opinion, I would like to know your thoughts.