On the Croatian conquest of the western Balkans and the incorporation of Avar tribes into the Croatian "state";
1) "Those same Croats have come and sought Heraclius, the Emperor, before the Serbs seeking protection from that same emperor Heraclius, and this at a time when the Avars defeated and expelled Romans from these regions... ..."because they were moved from Rome to this region, I think of those who are now called Croatia and Serbia. These are the same Romans, expelled by the Avars in the era of the same emperor Byzantine Heraclius, and their lands remained desolate. On the orders of the Emperor Heraclius, these same Croats defeated and expelled the Avars from those countries, with the permission of the Emperor Heraclius, they were settled in the same country of the Avars, where they now live." - Byzantine Emperor Constantine VII Porphyrogennetos in his work De Administrando Imperio
2) "Then the Avars, seeing that this is the best country, they settled in it. But, the Croats, who at that time lived behind Bagibareje, where they are now Bjelohrvati (Belohrobatoi)(White Croats/ White Croatia)... Of them(the Croats), a tribe separated, led by a bloodline of five brothers; Klukas, Lobel, Kosjen , Mouh and Hrobatos and two sisters, Tuga and Buga, came with their people to Dalmatia and found the Avars as masters of the country. They fought each other for several years, the Croats prevailed and killed some of the Avars and forced the rest into submission. And so since that time the country was occupied by Croats and in Croatia (Hrobatia) there are still descendants of the Avars, and they are recognized as Avars." - Byzantine Emperor Constantine VII Porphyrogennetos in his work De Administrando Imperio
To him the Avars were submitted after defeat and later assimilated into the Croatian proto-feudalistic/tribal structure.
The most important sentence is the last sentence that I bolded.
With it, Emperor Constantine VII claims that there are still Avars within Croatian rule during his time and that they are still recognized as Avars.
The "De Administrando Imperio" was written between 948 and 952.
Meaning that, within the timeline of this mod;
...so, how about them Avar units for the Croatian roster?