Maybe too late but the answer is Yes you can !
I faced the same situation today and got around it by doing the following –
Login to the vSphere Flash client (tested on version vSphere 6.5)
This is where you will do the trick. Open another tabin your browser and Login to your ESXi Host using this URL – https://ESXI_HOSTNAME/folder
Click on ha-datacenter-> Name of the datastore-> path to your file.ISO
Now right click on this file and click copy link address. Paste it in the URL field in above and pass the credentials. So the URL should look something like this –
I tested this with the HTML5 client and it did not work but works fine with the Flash client.