No. The Client cannot be modified - period. Hytale's Staff made this clear several times. If anyone somehow manages to do it, he/she will likely post some tutorial video, Hypixel Studios will find it, and then apply the fixes necessary to patch said vulnerability.
Deobfuscation cannot be patched since it essentially reverse engineering the client back to the unobfuscated source code and if studios like treyarch cant manage to fight it i doubt hypixel will be able to
Regardless, modding the Hytale client will not be something that's commonplace in the Hytale community. If it's even possible, very few people will likely attempt it, relative to the amount of people who mod Minecraft.
Modding will be very unlikely yes but where there is multiplayer there is usually a demand for hacked clients and since I think most people who are gonna play hytale come from minecraft I think its very likely that there is gonna be a hacking community