There is an issue with the current "skills_by_palette" specific to Revenants, which is making it impossible to determine which utility skill corresponds to which skill palette.
Revenants are a unique beast in that they use the same skill palettes for every legend: 4572 for heal, 4614/4651/4564 for utilities, 4554 for elite. Healing skills of all legends belong to the same 4572 palette, for example. 27220 is Glint's heal, 26937 is Shiro's heal, 27372 is Jallis's heal, yet they all have the same palette entry - 4572. However, the way /professions/:id "skills_by_palette" field is designed, it only allows many(palettes)-to-one(skill) linkage (i.e. you can find cases like
[ 4492, 55029 ], [4570, 55029], [4592, 55029], [4643, 55029]), but for this particular case we need one(palette)-to-many(skills) linkage which is currently not supported.
Without this it's impossible to create a full-fledged build template editor relying solely on data from the API. Currently only Kalla's skills have palettes assigned to them in /professions/:id.
I see two possible solutions.
1. Allow one-to-many scenarios in /professions/:id "skills_by_palette" field, e.g. something like
[ 4572, 26937, 27220, 27372, 28219, 28427, 45686 ]. This way, by combining the data from this field with the data from /legends/:id, one could determine which legend the skill belong to, and which palette refers to it under that legend.
2. Add a similar many-to-one (although in practice in most cases it's one-to-one) "skills_by_palette" to /legends/:id endpoint, that will define which skills belong to which palettes for that specific legend alone, foregoing the need to have arrays with more than 2 elements.