Assuming a pirate marauder build works the same as a normal one, It would be invented from the Nestor BPC and the build would include a Nestor. Build cost including invention at current pricing for advanced components would be well over 2 billion ISK (material cost to build a Kronos is currently about 1.7 billion ISK). That’s roughly 5 times the cost of a Rattlesnake for the hull but you won’t get 5 times the capability.
Are you sure you want to risk taking something that into a wormhole?