The mod is great, but performance is much too costly. As a suggestions, perhaps add modifiers to adjust the blast range and damage to make them more usable if the user wants to actually use these during a game?

Thanks for the comment.
When you say too costly, do you mean in terms of collateral damage, actual cost, or performance impact?

They are meant to have massive collateral damage, although the 5 and 20 ton yield bombs are pretty limited, and other bombs are unrealistically small, real bombs range up to the hundreds of kilotons.

The actual cost of the items, from what I have found isn't too bad, they should always be hand deployed, so it's not too hard for a big factory to produce many of them.

If you mean too much of a performance impact, I kind of agree with you... Until recently I was using this on a gaming PC, and that had some lag issues, but was mostly OK, and I figured that it would be a mod for high performance computers in any case. There are many optimisations in the code, but executing the lua scripting is just inefficient and slow. There are sliders for the Hiroshima bomb, to limit its effects as I was worried it might actually crash the game, so I might add more sliders for the other bombs.

From your perspective, what is the biggest performance problem?
There are four causes of the lag when detonating a bomb:
1: the instantaneous lag, which briefly freezes the game entirely, this is the thermal damage being applied, and the map loading in.
2: the lag for some small amount time after the weapon detonates, this is largely caused by the fires lit around the map, and lasts less than 10 seconds (depending on how slowly the game is running)
3: the lag for about a minute, as the blast wave expands, which gets worse over time, as the wave get bigger. This is probably the worst part of it, and really kills the frame-rate.
4: any residual lag for the next 5 minutes as the radiation clouds linger around, and the longer burning fires go out.

Other than that, I can only recommend turning off the "large number of short lived fires" in the map level mod settings, and using nothing larger than the 500t nuke.

Alternatively I could just add more lower wield artillery nukes, e.g. a 200 ton

This was before your recent update. I'll have to test the update out.

In multiplayer we tested two nukes, the small 100 ton? Artillery shell, and the atomic rocket. The artillery shell caused a fair bit of destruction to the biter test site, however the destruction was not really worth the lag generated in my opinion.

We then tested the overridden atomic rocket. We used a helicopter as the delivery method since handheld deployment would be suicidal. Upon launch, the helicopter was turned around. On impact, the server lagged for probably 5 to 10 seconds, but recovered. What didn't recover was controls for the helicopter. Due to the lag, inputs given to the helicopter from the client were either delayed or not received. The blast also set the helicopter on fire. The pilot attempted navigation to a repair Warden from AAI, but couldn't fight the controls before the helicopter burnt up. This meant that with the mod, the atomic bomb rocket was undeployable, and usage of any other nuke required coordination between other players due to lag. We also attempted the hiroshima bomb on a local server just for the giggles, but the server ran out of it's 16 gigabytes of memory and crashed before full simulation was done.

Thanks for the response.
A few things then about this. The new fire-shield is intended to avoid these situations, as I encountered them when trying out the Aircraft mod myself. Besides this, the range of the atomic bomb has now been increased. Most of the lag experienced from the 500 ton (and above) is from the map loading, as the game has to generate a huge area of map.
When using even basic power armour, the atomic bomb can be survived, and using more advanced power armour allows relatively minimal damage.
The spidertron works really well for deploying them, and can get away with burst-firing at near max fire rate (if your computer can keep up), the new update also brings a specific bonus to aircraft for firing nuclear weapons.
If you experiencing lag (and particularly memory) issue when using the weapons, then go into the mod settings (on the map level), uncheck the "nukes cause lots of small fires" and set the fire-reduction and blast reduction settings as high as they go, the fires use a huge amount of memory, but are enabled because they look cool, even though they don't do as much as some of the other features. The performance testing has all been done on relatively capable machines running the game locally, so a server may struggle much more with lag issues.
As well as this, you may want to try out the new really really small nukes, which produce much less lag.
Other than that, I am limited by how fast the lua scripts will run, as the game isn't all that quick at them, but if you still experience problems, I am trying to improve things for the next update to allow the 100kt nuke to run... but these will improve the 15kt as well.
Thanks again, and sorry you are having trouble.

I played with the mod in multi-player recently, and I found that the lag issues are much worse for the client to a server than on the server itself. I can't really do that much about this (and am honestly impressed it doesn't desync, even in those conditions).