These 'pets' beauty are on the same level as her.

Ufufu, you have one great mind my friend. But I'm not gonna confirm your thought now since most of Andras Kingdom technology and research will be explain in the next few chapter.

Sooner or later his delusion will merge with his soul so it obviously not external force (I think). But if you think that his delusion is external force then shouldn't that mean his vision also external force? After all, Vision is a gift from the gods. Meanwhile the delusion is gift that Allen get after becoming a harbinger. So you want Allen to rely on his physical ability and swordmanship alone? Don't be foolish, in a world like that it's ridiculous to fight an enemy with just physical power. But if Allen just forced himself to use his physical power and technique in a hope to become stronger, then I think Allen is big idiot to not use such a power that was being bestowened to him. Even the Traveler use the elemental power she got after resonating with the statue of the seven. Also I think Allen is not arrogant but he has pride for his talent.

Will Allen recruit some playable character to join the Fatui and make them his subordinate?

Is delusion of the Harbingers special? Previous chapter back then, Pierro order Ajax to find the true 'Tartaglia delusion'. From his words alone we could tell that the delusion Harbingers used are special compare with normal delusion. So I just want to ask what makes it so special? Also, your choice for making Allen fight Columbina is very surprising. I thought she is a catalyst user. Although it seems like she is not pure sword wielder since some of her attack seems like she use catalyst. Anyway good idea

If Allen follow Pierro's advice then he will most likely fight the strong one. But unlike Ajax, Allen would choose the strongest sword user to make his talent more bloom. As for who, I don't really know. I lack information regarding the Eleven Fatui Harbingers wether in canon (Except Scaramouche and Signora) or in your fanfic, so I couldn't predict it well enough. There is a video in youtube about the Harbingers fighting between each other. But sadly, it's fanmade so I can't use it as data base. But in my opinion, I think he will face the Tsaritsa like Ajax because, back then Tomoki said (If I remember correctly) to Allen that the Tsaritsa showed him a new level of a swordmanship. So yes, I think would fight the Tsaritsa like Ajax and most likely he will lose miserably and he needs four years again to become a Harbinger. (Sorry if some of my grammar wrong will hurt the eyes of those who read it)

I don't think so. I remember Kazuha take that delusion after the death of Tomoki