One of the major problems with anti-nukes is that you have to judge how many you will need based on having intelligence on the number of nukes possessed by your opponent. Guessing too few means that you lose your entire base instantly. Guessing too many means you waste a lot of resources in a way that doesn't benefit you. I propose an orbital unit that can destroy an infinite number of nukes, so long as it is positioned above your base. This will provide incentive to fight orbital battles to destroy anti-nuke satellites in order to land nukes on the enemy base. The point is that the satellite can destroy unlimited nukes, so long as it remains alive in space. It should cost maybe as much as 2 nukes. This way, you can build an anti-nuke and then upgrade to the satellite. Losing the space battle then means that your opponent can nuke your ground base. With the orbital radar, it is obvious when your opponent is attempting to mass space. So scouting is easy enough.
Orbital Anti-nuke (or in general anti-missile if we add catapults or other possible missiles in game) installation would be useful addition but I think that it would be rather not such wonder weapon like OP suggest, it could shot the missiles with energy beam, but it would be rather slow to recharge, so it would destroy one missile at a time and had moderate recharge rate , so it could work when enemy would throw at you single nuke, but it wouldn't guarantee you 100% protection against nukes, so probably you could need entire battery of those to be shure. Also It's durability and ground coverage could be inferior when compared to anti-nuke (witch could be a notch larger, BTW). To had good defense grid you would need dozens of those covering your sky, so I suspect that it would be much cheaper and cost effective equivalent of anti-nuke missiles, but if they would be as much as durable like orbital radar, they wouldn't last long if enemy had sizable force on orbit... actually we could send one anchor per satellite spot and your opponent would most likely enjoy nuclear winter 10s later (or less).
Anti-nuke satellites should be used for planet invasion to prevent your beach head being nuked instantly.
