I have experimented with a couple of 'natural' preservatives - grapefruit seed extract and alcohol. The lotions were fine under some conditions, if certain essential oils were used in the lotion (at low concentration), and if the temperature was not too high. I suppose one could devise a combination of essential oils and GSE or/and alcohol - and tell the customer to keep the lotion refrigerated - with an expiration date. I actually have customers asking me to do this. It is not impossible, but it would be such an amount of work that I politely refuse, and gave up that part of the business.
Also, there have been concerns on solvent residues in the extraction of grape seed extract, so not all 'natural' is benign, or truly natural. Alcohol needs to be used at a high enough concentration, so that brings its own set of problems.
I read the MSDA (Materials safety data sheet) for one of the germalls which I bought and did not like it, so I decided to do without. To me this means no more water/oil emulsions, so no lotions. Once you mix water and oil, bacteria, fungi and molds like to live in it.
Now I just make solid lotions or salves, they work great and require no preservatives. This is now all I use myself. They do not sell as well as the lotions, but they do sell. Anhydrous products are ok without a preservative, but you can get rancidity depending on the oils, different story, vit E can help there.
Since you are thinking about a business, I will also say that another reason I dropped the lotion making, was that I had to work 4 times longer for a dollar than when making soap.