My Take
1. Plausibility for an Aromanian State: low.
2. Most likely area(s) for an Aromanian State: South-Eastern Albanian Epirus + North-Eastern Greek Epirus + Westernmost Greek Macedonia (Pindus Mountains) + Southernmost Yugoslav Macedonia.
3. Name. Let's make a distinction between endomyms and exonyms here. Examples: Finland / Suomi, Georgia / Sakartvelo, etc.
Romania is
România in Romanian and
Armâñia in Aromanian. Yes, we the Aromanians call ourselves Armâñi and we call Romania Armâñia!
So, it is obvious that an Aromanian State would be called Armâñia in Aromanian (the endonym). OTOH, its English exonym would probably be Romania (if it is before the creation of a united Romanian State north of the Danube with this name). If Romania is already taken (by OTL Romania or by a Greek State, Ρωμανια), then the Aromanian State could be called in English Aromania.
If the local name Epirus is used, the English exonym would be obviously Epirus while the Aromanian Endomyn would be the Aromanian term for it, Epiru.
4. Proposed territory (with an Aromanian plurality at least until the Balkan Wars), see map:
5. Capital: Moscopole (although very marginal, see red dot) or Bitolia (Bitola), Grebena (Grevena), Castoria (Kastoria) or Curceaua (Korçë).
6. Area: cca. 15,000 sq km.
7. Population: cca. 1 million (Aromanians 40%, Albanians 30%, Greeks 20%, Bulgarians 10%, without the 20th century massive Aromanian denationalization).
Disclaimer: I am Aromanian.