I'm planning to use single-color SVGs for my menu and toolbar icons. I've been looking at TMSFNCSVGImageCollection as well as this one: https://github.com/EtheaDev/SVGIconImageList
The latter one isn't cross-platform but does have a nice FixedColor property in the collection that makes it easy to change the colour of the SVGs. It would be nice to have this in the FNC collection.
TTMSFNCSVGImageCollection is also not cross platform, VCL only. If you want to have a cross-platform container, you can take a look at the TTMSFNCBitmapContainer. The bitmapcontainer works with FNC components. It does not work with default FMX components however, but you can easily retrieve the added SVGs by name.
There are currently no plans for a cross-platform version. TVirtualImageList which uses the TImageCollection is VCL only. There is no FireMonkey equivalent of the same class unfortunately. This would mean you'll need to manage 2 separate components. Also, FMX stores the images in a different format compared to VCL, so unless you create them programmatically you cannot share them between frameworks. We'll add this on our feature request list.