It depends on what are you looking for. Bhikkhunism is mostly to expand on the girls' personalities and fill some holes of the game's narrative. For example, chapter 2 explains why one of the girls is dressed like a maid and a later chapter reveals a pretty interesting connection to Mermaid's bad guys.
I guess is more accurate to wonder if Bhikkhuni will top Mermaid as whole.
While it is true this is a companion piece for the game, I think it can be easily enjoyed on its own. Since is basically just fluff pieces to explore the game's setting and the characters a little more, so the only thing you really need is to be familiar with the basic concept of the franchise.
The only exception is chapter 5 since it drops a pretty important reveal fr both Bhikkhuni and Mermaid.
That said, I'm enjoying the character interactions a lot. The girls are just so adorable.
Amusingly, on /u/ Bhikkhuni went from being a "shitty waifubait SK clone" to "better than Mermaid" as soon it was confirmed that yes, the girls are really, really gay.
To be honest at first I didn't really like Bhikku initially, mostly for the character designs because they all looked too similar to each other compared to Mermaid. But this manga, and well as the upcoming game, have really made me soften and like them more.
Looks like it. In Mermaid, an ecstar determined what kind of weapon they turn into, Maybe it's different for Bhikkhuni? Since they are all reversibles, and it was a rare trait in Mermaid. Different V-virus strain?
Yeah, here in Bhikkhuni the Liberator will always get the same weapon regardless who their partner is. Although according to the prowess of the Ecsta, they can achieve different upgrades for said weapons.
And indeed, the Bhikkhuni cast is infected with a rare strain called VR-Virus. That is why they are able to be either Ecstar or Liberators.