I think you may run into difficulties with this. Since potion id's are stored as bytes and not integers in minecraft code, any id that is 128 or above will give you crashes, wrong potion effects or null pointers errors. Others have tackled this issue and to do it properly, you would have to change how minecraft stores potion data entirely. I know of at least one mod that uses byte transforms to change the data to integers.
If you want to test the robustness of your code, add mods to your dev environmnet that would put you over the 0-127 limit and see what happens. As I mentioned previously, this seriously caused me a lot of frustration tracking down how different mods were handling potion id's above 127 in a modpack I am putting together. Unless you want to add to your programming workload, you might want to consider not supporting this element and rely upon other mods such as Extend Potions to handle this.
Minecraft 1.9.x+ handles potions differently now, so this is not a problem anymore.
Feel free to open an issue on the EvilCraft issue tracker about this, I can't promise when I can look into this, since 1.7.10 is not our main target anymore.
I'll look into it.