Like most redox/flow batteries they have a very big shortcoming and that is a very limited operating temp range for vanadium it’s 10-40c that means they’ll need environmental controls installed in almost every case.

Given that these batteries would be used mostly in stationary applications, where space is less of a problem, the only question is how much extra power would the heaters and/or coolers need, and how much waste heat the charge/discharge releases (some of the waste heat could be used instead of the heaters, but would put more demand on the cooling system). Unless the amount of waste heat is too high, it doesn't sound like too much of problem to me; given proper insulation, most of the heat would come from the battery itself.

Cooling/heating Li-Ion batteries which have a wider range and are mechanically easier to cool than liquid Redox batteries is a big challenge, this one is a much bigger one.

Li-ion generally needs HVAC too, and if you only need HVAC at 104F that's not too substantial a cost for southern (US) solar available regions.

Modern Li-Ion can operate at 0-45c in "fast charge" and there are even higher ranges being developed, there is a huge difference between 10-40 and 0-45 as far as suitable environmental locations go.

Li-Ion can be charged at 0c or even below in some cases, with Vanadium Redox you get crystallization at 10c and the battery stops working it's not like Li-Ion where you lose some charge and you need to charge at a lower current and the charging it self will bring back the inner temp of your battery pack to fast/full charge levels.

For grid storage, density is entirely a non-issue.

Salt water battery looks better: https://en.wikipedia.org/wiki/Salt_water_battery

That article is very low on actual electrochemical details. Here's one of the research papers on high performance salt water electrolyte batteries: http://sci-hub.tw/10.1126/science.aab1595