How can current EB-2 visa holders fulfill EB-5 investment requirements?

What you propose may work. But the largest question is how much are you spending on job creation and how many jobs will be created by your investment - or how many new jobs have been created so far?

No need to switch; you can stay in both queues at the same time and withdraw the second one once one is approved for permanent residency.

It sounds like you are referring to the E-2 (investment based visa) - you can use your investment in the E-2 entity for EB-5 purposes so long as there are detailed source of funds documents to prove the origin of your investment. The corporate structure of your E-2 entity is also important - jobs must be created and employed by the entity that receives your investment or any 100% wholly owned subsidiary companies. You should speak to an immigration attorney before filing the EB-5 petition to make sure all relevant requirements are met.

There is no need to "switch" from an EB-2 to EB-5; a single foreign candidate may have both processes underway at the same time without contradiction. Note, however, that the EB-5 process cannot "borrow" the EB-2 process priority date. (This is a significant difference from EB-1, EB-2, and EB-3, which all may "borrow" each other''s priority dates. The EB-5 process uses its own priority date, which is non-transferable across other EB processes.) Regarding the investment amount, as a preliminary concern, the USCIS will likely require you to show how the invested funds will create job opportunities, not just purchase inventory and warehousing and equipment. It is recommended to consult with an experienced immigration attorney to assure as far as possible that your EB-5 investment plan can credibly result in the necessary job creation.

In addition to the investment in a new commercial enterprise, you also have to create 10 full time jobs. What is the plan to create the jobs?

If you are not creating ten new jobs, it will not work. EB-5 is for job creation.

I presume you are referring to a change from an E-2 (not EB-2) to EB-5. Yes, it is doable.