It is not true that it cannot be used as system or bootable disk. And disappointed to hear you don’t have any confidence in Sandisk products. I mean with a warranty of 3 years and with a pricetag of higher end SSD drives, it should be able to handle system disk standards.
If I am not mistaking, there is a SATA drive inside the Extreme 500, a drive of the Plus series, should be able to withstand constant read/write for many years, or correct me if I am wrong?
Read in a rewiev that Sandisk confirmed that the Extreme 500 does supports TRIM, but then again I read allot of people saying it cannot be enabled on USB drives, so am a little confused, and not much details on Sandisk website for the Extreme 500 SSD.
EDIT:
Image of the inside of the Extreme 500 SSD, does appears to be a SATA drive:
