Has there been discussion or indications of using UUVs as mobile pop-up radars? Such systems could pop their heads over the surface anywhere, scan the sky for aircraft, potentially cueing VLRAAMs to target, and go back underwater before being destroyed. They would complicate enemy aircraft deployment patterns due to having no way of predicting when their formations (especially tankers/AWACS) will come under detection range.
Many issues with such a system.
Firstly would be power. Radars, especially long range ones, require huge amounts of power. Unless you want to add mini nuclear reactors to these, the availability of onboard power will be a major limiting factor.
Secondly would be survivability. These things are slow and rely on stealth as their primary defensive measure. Surfacing and popping off radar will immediately give away their location. Even assuming opfor don’t immediately engage it with an ARM, which they can easy carry as standard after the first time you pull this trick, once the location is know, opfor will have a much easier time hunting these down with ASW assets once they know where to focus their efforts. Basically these will become disposable radars that you use once and expect it to be destroyed soon after. Making it massively uneconomic.
Lastly is just the need. Why go to such lengths to get a surface radar deep into the ocean when you can just use AWACS, UAVs, satellite and many other available existing assets to get the same or similar enough radar picture without the costs and risks involved in using an unmanned sub.
Using the UUV like this is like suggesting you load army tanks and artillery onto cargo ships to provide fire support. Sure you can do it, but why would you bother when you have far better and more suitable assets to do the same job better already?
The only scenario where I can potentially see putting radar on a UUV as somewhat worthwhile is if you also add in VLS launched SAMs as well, and have these operate as hidden anti MPA bastions for your manned subs (since they will almost certainly lack the speed and endurance to keep up with manned nuclear subs).
So, if one of your manned subs gets detected and is being actively hunted down by enemy MPAs and ASW aircraft far from friendly land based air or naval support, it would be worthwhile to surface one of these to spam SAMs at the airborne hunters to save your manned submarine, even at the cost of the UUV. But that will require a much bigger UUV unless you make SAMs that can be launched via torpedo tubes or some sort of erection launch system.