Where was the CSA going to get the engines for a fleet of ironclad warships? As we know, many of the CSA ironclads that were built had clapped out engines salvaged from other vessels. There were no engine building facilities in the CSA.
A City Class gunboat burnt a ton of coal an hour. Even churning their wheels as hard as they could go, a tugboat was needed for them to move upstream on the Mississippi. Coal barges were lashed on both sides to provide enough fuel for moving from point to point. Even the much lighter tinclads burnt hundreds of pounds of coal per mile. Where were all these new ironclads going to get the mountains of coal they would need for routine operations? Where were the coal barges & tenders needed to keep the ironclads at sea going to come from?
Steam engines of the 1860’s required constant maintenance. As we know from the history of CSA ironclads, a lack of parts & engineers to install them kept exiting CSA ironclads tied up for weeks & months at a time. Where were the mechanical, logistical & support elements of the iron clad fleet going to come from?
Steam engines don’t run on automatic. They require constant attention by skilled firemen & engineers. There weren’t all that many steamboat men loyal to the South. Assuming they managed to acquire enough engines to equip a fleet of ironclads, where were the skilled engine crewmen & engineers going to come from?
After the pursuit of Hood ended, Grant ordered an entire army corps transferred from Bridgeport to New Orleans & then Mobile Bay. 40 tin clad gunboats escorted the transports. That was about 15,000 rations / day for soldiers & riverboat men. About 3,000 equines @ 26 pounds of fodder/day = 76,000 ponds a day. That is what a real strategic brown water fleet looks like. US Army Quartermasters had 11,000 brown water & littoral vessels available to support army & navy operations.
A few CSA ironclads capable of 5 knots at the best of times would have consumed vast quantities of scarce resources. At no time or place could they have been capable of doing more than annoy the littoral & brown water assets of the USN & army.