This what you are saying has no historic, nor archeological backup.

Firstly, you cannot make connection between phenotype and haplogroup, although from Illyrian sites, majority of skulls were long headed, thus not dinaric.

Iliryans were relatives of greeks,and greeks as well as albanians dominate in E and J haplogroups.

I2a2 and R1a spread into Greek territory corresponds with Slav invasions, and migrations.

The part that you said, that there couldnt be any major migration, is complete BS.

It would take a week max to come on foot from region of carpathian mountains, and thus no evidence or trace would be left anyways.

If it makes you more satisfied, Serbs have similar composition of haplogroups with Albanians and Greeks, although you are all very very heterogamous and mixed which is not suprising since you were all in center of cultural and national melting pot,  there are  probably are a lot of Serbs with Illyrian roots.
And all of your 3 nations have predisposition for assimilation acts till this day, and thats the other way to explain it.

Most of latinized Illyrian people from Cro-BiH region, ended up in south Romania during roman times(which turks settled in BiH later on, as vlachs, later known as Serbs), and those latinized Ilirians from Croatia, like Ćići from Istria, who were settled there from Dalmatia, have very minor I2a2 share, less than 10%.