Not to mention, even if this weren't potentially a violation of one or more intellectual properties to make your own mod pack and then ship it out to one or more people without consulting the modders, it's also a nightmare and a half to assemble. Lots of mods will have conflicts with their IDs, and both 1) having those conflicts resolved and 2) leaving space for future mod updates which would add new items takes a long time, not to mention adjusting the configuration files to your liking.
This is why FTB takes so long to update even once all of the mods are updated, as the team has to take into account any and all new blocks and items, any and all new features along with previous blocks/items/features, make sure that there are no item ID conflicts, make sure there is enough space for future IDs, make sure that the configuration files are compatible and the mods work together and make sure that the config settings set the right difficulty. Only then is the pack ready for release.