set file_contents (cat filename | string collect -N)
I understand that this is purely anecdotal, but I'm using fish for quite a long time, I've written a lot of tooling for myself in fish, and I agree that sometimes there are some things which are annoyingly missing from fish (like this multiline variable thing), but I would not say it makes fish significantly less powerful. And these things are sometimes fixed, too.
One possibly unobvious thing is, though - there are only three grammatical genders in Russian, so all words which do have gendered forms can have at max 3 of them (male/female/neuter). This means that if you do allow more than 3 kinds of pronouns, you’ll probably have to define the pronouns->grammatical gender mapping somehow. Well, I guess plural variant also counts, so maybe 4.