Using a VMware virtual disk as L2ARC read cache?

I have the following server:

• T330
• Intel Xeon 1240 v6
• 32GB (soon 64gb) ECC
• 1x4TB via H330 controller (soon 7 more slots, so might go for a nice 6x4TB raid 6)

I would like to know if it would be a bad thing to use create a virtual disk on the the Samsung Pro 960 NVME and use that as read-caching (L2ARC) in FreeNAS. Currently my biggest problem is a lack of PCI-X slots that are too small or too big. I got 2x WD Black PCIe SSD 256GB on Amaszon Prime Day, but will have...

Using a VMware virtual disk as L2ARC read cache?