I need to remove duplicate cells but besides specifying which cells
constitute a match I want to specify what to do with conflicting values in
the duplicates.

For instance one thing I'd like to do for some cells is combine/concatanate

So if I was merging on Field 1 but wanted to concatanate field 2:

Cat | Brown
Cat | White
Dog | Spotted
Dog | Striped

I'd end up with

Cat | Brown; White
Dog | Spotted; Striped

Likewise if I just wanted one value I'd like to use another field (e.g.
SourceField) to do so. So in the same instance if I wanted to merge/remove
dupes on Field 1 and use the values from Field 2 where value in Field3
(Source) = "Library"

Cat | Brown | Library
Cat | White | Wikipedia
Dog | Striped | Opinion
Dog | Spotted | Library

I'd end up with

Cat | Brown
Dog | Spotted

Are these possible with formulas?