Creating a tool for this would be unwise unless it could repoint data, either automatically or by prompt. Otherwise the tool would likely be unusable, as evolutions do not consist of a constant number of bytes—some are three, some are four. In addition, they are intermixed with move/level learning data.
If a tool like this were made which supported repointing, it would be able to avoid the above problems and allow dynamic changing of the
number of evolutions, not just what they are. This would be extremely useful, but I don't know if any of Swampert's tools support repointing (having never used them).
In the meantime, you can edit evolutions in hex.