I'm the ST in this case, and my purpose actually IS to let Lunars use Wyld-only Charms.
Are you actually running 2E?
Why? Do you not like having SAN points? Run it in a rules-light system of your choice. You'll have a better time.
Joke aside, and if you're really committed to this for whatever reason, what you need to do is something along these lines: throw together the known strong builds (2-7 filter Claws of Silver Moon martial arts build, 2-7 filter killstick build, 2-7 filter giant kaiju build, 2-7 filter flying archer build), remove the obvious broken exploits in the normal charmset, then add unrestricted use of Wyld-only effects to your test builds and see if anything breaks with the expanded capability set.
Things you need to nerf straight up before you do anything else: the charm that lets you get motes back for breaking random scenery (for obvious reasons) and the charm that gives you one attack per limb in a game where you can turn into a giant centipede (for obvious reasons). There is also a reasonably solid textual argument for double-dipping Excellency efficiency via Accuracy on Claws of Silver Moon (Dexterity Excellency to boost Dexterity for purposes of defining CoSM's Accuracy, Dexterity Excellency to boost your attack roll), nerf that right quick while you're at it before anyone gets funny ideas. Kill charmsharing wherever you find it to make your testing burden bearable, delete the "Lunars can buy raksha charms" thing or you're going to end up in combinatorial testing hell.
You also want to kill player access to broken material from shoddy sourcebooks like the merit that lets you use Strength for to hit rolls in place of Dexterity or Scroll of the Monk charms, also for bleedingly obvious reasons.
Get your example test builds, do your changes, add Wyld charms, observe for obvious broken interactions, stop if you run into something particularly terrible. Effective ways to break dice caps on attacks or DVs, reduce effective Speed below 3, generate free motes and/or willpower, perfect cheaper than 3 motes and making attacks unfooable/perfect cheaper than a defending perfect are an example of "something particularly terrible". If you don't run into anything terrible, feel free.
If you're using the 2.5 errata, the same advice applies but with different numbers involved. The process is identical.
Also, something you might want to do is to just make the Wyld-only charms just work but cost more or have a lesser effect in Creation by default rather than bother with even more charm purchases required to unlock functionality in Creation. By RAW you get one charm roughly every two sessions, if we assume one session a week that's a lot of dead time spent buying things that don't work individually.
