There is no "easy way" to get your greencard when in E2 visa status. Actually, when in L1a status it is a lot easier since you can skip the Labor Certification process. It is often very difficult for E2 visa holders to obtain greencards which is particulary the case when they own a majority of the company that sponsors them. The E2 visa also lacks the dual-(immigration)intent that is allowed with H1b. I have heard of one suggestion in which an E2 company grew its revenues to US 1 Milllion and then tried to go for the EB-5 immigration category.
Personally, I find the E2 visa one of the most flexible. It can be extended indefinitely (with 5 year increments) as long as you satisfy the underlying rules. Also, your spouse is allowed unrestricted employment authorization.
I suggest you discuss this with an immigration attorney with experience in E2 visas.