I have been liking Agnieszka for some weeks, what do you think of it? I also like Agnes and Agnese, I pronounce them ah-nyes and ah-nyese (as it is regular in my country / language).
(I am not naming a child, this is purely hypthotetical and for namenerd passion?)
Would Neske / Neska / Ness / Neshka / Neshke be reasonable nicknames?
Would it pair well in a hypthotetical set where the other two middle names are (first) Liselotte and (first) Swanhilde?
[name_f]Agnieszka[/name_f] is distinctive, sharp and bold but with a sort of warmth to it too.
I think all your nicknames work and that it would pair well in that set
[name_f]Agnieszka[/name_f] is so romantic and pretty, and she fits so so well with [name_f]Liselotte[/name_f] and Swanhilde!!
I think all of the nicknames work well, and Neshka is probably my favorite!!
[name_f]Lovely[/name_f] picks as always 
[name_f]Gorgeous[/name_f]! I love it! It’s a little bit stronger then [name_f]Swanhilde[/name_f] and Lieslotte, as they are both very soft in my mind, but her distinctive flair, length, and uniqueness definitely fits!
The nickname used for [name_f]Agnieszka[/name_f] in Polish is Aga (or, occasionally, the very familiar Agusia). The others would not be used in a Polish speaking context.
It’s very common in Poland, so it doesn’t feel special or distinctive to me. Feels common, quite soft
[name_f]Agnieszka[/name_f] is sweet, bright, romantic and familiar. I really like this name and she’s within my family tree so I really like her. She makes me smile and feel nostalgic. I think your nicknames do work but I know Aga is most common (my auntie is known as Aga)
I think she works well with [name_f]Swanhilde[/name_f] + [name_f]Liselotte[/name_f] creates a very grand, intriguing sibling set.