YodaMaster said:
We try to model historical alliances between Moldavia and Wallachia, Alexander I for example in 1431, but this is not sufficient to form a united country according to our historical standards.
Wallachia starts with core on Banat, Transylvania and Dobrudja.
As I understand this post (however I hadn't got much vein to read it deeply

), the approach to this topic is completely false. But I wish to divide things to separate lines.
1) the request is that there should be an event to create a national state. This would be IMHO completely ahistoric, because before the nationalist era no one thought about these concept.
1b) the role of Mihail Viteazu (Vitéz Mihály in hungarian, Michael the brave in english): he is not the first one who was able to unite the romanian lands, but he is instead one of the most successful wallachian rulers, who was able to extend the borders of his personal demesne. It is very important to understand: nationality at that age was not the primary idea which organized countries, because the 16-17th century societies did not consider it as a community forming factor. Rights from birth, the classes of the society, and religion were much more important.
2) the role and situation of transsylvania:
2a) transsylvania existed as an independent state and a political factor from 1541 to the 1690's de facto, and to 1867 de jure. there was no independent transsylvania before this, so I find it quite strange that it is an independent state before 1541 but I can live with it at least I mod my installed version.
2b) demographics: according to different sources, the majority of the population till the 1660's was hungarian, it changed after the 1660's because of the destruction after different wars, and from that time the majority of the population was romanian. This has two main reasons: the first is that the romanians lived in the relatively safer upper parts of TRA, and there was an immigration from moldavia and wallachia after the turks were driven out from the carpathian basin. It is also important to say that the ethnic changes of the peasantry did not changed the ruling class and did not have any effect on the union of Kápolna, so the nobility (which was mostly ethnic hungarian), the saxons and the szeklers remained the only political factors of the country till 1867 when transsylvania was reunited with the other parts of kingdom of hungary.
2c) the main goals of transsylvania's foreign policy: in 1541 the ottomans occupied Buda but before this the country already fallen to two parts. the conquest of Buda just caused that the followers of king John I. were forced to move their capital to transsylvania, while the centre of the followers of Ferdinand I. remained in the western and northern part of the country. from this point there were two goals for both sides: drive back the ottomans, and defeat the other faction. of course the "kingdom", which was ruled by the habsburgs had much more resources, but transsylvania was a relatively free ottoman wassal, so if it was necessary they had support from the ottomans. so in this situation there were two goals for transsylvania:
a) get back as much territory as possible from the kingdom of hungary, and get back the king title from the habsburgs
b) and after that get rid of the ottomans and unite the country.
in this situation the two romanian principalities were counted as possible allies and vassals, but it was meaningless to expand to that territory.
3) the political connections of the two romanian principalities and transsylvania/kingdom of hungary (before 1541):
these connections are quite ambivalent, however in general were much better than the hungarian - romanian connections nowadays.
Of course the different religion and the constant hungarian attempts to gain more control above the two principalities caused many conflicts. But it is important to say that the wallachian and romanian nobility was always invited to the kingdom's diet, and after the fall of the kingdom to the transsylvanian one, the nobility was counted as the part of the nobility of the kingdom, and despite the ottoman influence, they always tried to help their christian buddies against the moslems if it was possible. sometime with just some information, sometimes with force. of course it was not easy with the ottomans in their back.
I wrote much and I hope it may help with some information.