I had an idea for a new upgrade type called the workers/mercenaries. I don't know exactly what category they'd fall into, weather it be normal, heavenly, or a completely new type with a new currency, but what they'd do is boost your CpS by a specific %. They's have different levels that'd give you bigger boosts. I'll give you an idea as to what they's be like:
LvL 1: +1%
LvL 2: +3%
LvL 3: +6%
some ideas I had for different people are:
Engineer, Hacker, Bodyguard, Doctor, Explorer, CEO, etc.
Another idea I had for this would be that it would be like the pantheon, in which you could only use 3-4 people at a time and each one would have a special effect, but they wouldn't have downsides.