There can be company which can be in industrial and modern era. These can be start by you which we can also use to construct units but difference is they will have technologies which give a bonus which will give you advantage but these companies will ask gold for it.

Ex: Your company develop a better armour for tank which give you special benefits like better defence.

A bullet proof jacket which cause decrease in damage of units.

My main idea is main thing is it prevent snow balling effect and to tackle players which only have big army with no speciality.

If your company have special technology which give you a way for your income. You can restrict your company to share benefits with other civ or not.