I think chances are Spain would definitely be more conservative. Queen Maria Christina only became "liberal" when she needed their support against her brother-in-law and she never really showed any real subsequent support for them. Chances are she'd ignore them and they wouldn't have any real role in Spanish politics for a good while.
I agree with you, at least partially, on this one. Spain was wrecked internally and needed to rebuild its infrastructure and economy. My question is could industrial modernization happen with a conservative, absolutist government. Personally I think its possible, once those at the top accept it. Look at Russia, its Tsarist system was the most absolute in Europe but by 1914 it was well on its way to outdoing even Germany's industrial complex. Assuming that there are at least a few conservatives who can see the value of industry, then chances are Spain would follow OTL Isabelle II's reign in terms of railways, telegraphs and other industries.
Portugal is one of those I see as a major key in the region. Even if Anglo-French support continues, Spain is in a much better position to give aid. From what I can tell Portugal's situation at that time was basically a standstill, with both factions dug in. While the Miguelists did OTL surrender, that could change with Spanish support. At the very least they were in a position to maintain control of a good half of the country if they chose to dig their heels in. Really the key would be to continue the war until Britain got sick of it and disengaged. Orléans France on its own wasn't in a position to continue the support.
So basically, if the cards are played right, we could see a French Legitimist movement backed by conservative Spain and Portugal. Could be highly interesting.
Again, assuming the French even would support the Liberals ITTL, which since it's Legitimist, would not.With Franco-Spanish support, really like you said, it would only last as long as Britain isn't tired of the fight and quits the war.
However one thing I should take of note though, is the potential threat of an 1848 analogue. Obviously of course, the idea of Absolute Monarchy isn't going to be favored for much longer in the face of Social Democracy. Even if we're going to go for a Limited Constitutional Monarchy (of which the closest analogue to this would be the Kingdom of France itself at the time), there will still be the issue of the belief that either King should reign and not rule, or worse, that the monarchy as an institution be removed as far as Spain is concerned. This will be something that will need to be settled with upon the accession of Ferdinand VII's male successor to the throne.
Another thing I should actually make a case of, you said that industrialism is key, and you are right, as the economies of Britain, France and Prussia was helped by the industrial revolution. Now the issue is, where are we getting the Spanish industrialists from? Spain has the resources, it had coal and iron, two major components needed to develop industry along similar lines to the above mentioned countries. It also had a textile industry in Catalonia, but that's about it.
Long story short, it will need to find ways to placate the masses, have the liberals in government without them utterly changing the system too ridiculously, and also build the crucial infrastructure needed to develop Spain economically.