I have to use my own developer account basically every time I build an app for a customer until they got around to either inviting me to their team or creating

I have to use my own developer account basically every time I build an app for a customer until they got around to either inviting me to their team or creating their personal developer account. Unless Epic is filled with developers that never ever launched their own application not being part of the Epic developer account is an annoyance (and a familiar one for most iOS developers) at most. You don't need to deploy an SDK the only thing you would deploy are test builds of games that use the updated SDK.