Impingerment freezers focus air flow and use a lot of fan horsepower to get an inline air-based freezer up to the capacity of a cryo freezer of the same lenght and width...But getting a spiral to the same heat transfer as an impingement freezer is not going to be easy, and may very well play hell with your enclosure.
Whether or not there is much to be gained is pretty easily identified...but compare Spirals to Spirals.
How much you can achieve with sheeting and baffles and more fans can be "modelled" by comparison with the most efficient models of such freezers...If you've got one made by somebody other than Frigoscandia, compare its real heat transfer per square foot of exposed and product-covered belt with that of a current Frigoscandia; then compare your fan horsepower with that of a current "high end" Frigoscandia. It will set your target for you in a hurry.
By the way: Too dense a belt loading will make your freezer go through the top of its efficiency cureve, and the higher the freezer performance is, the greater the downhill slope of that curve...
Of course the easiest way to get more out of it is to make it operate colder, and that has the added benefit of reducing shrink and distortion. That approach means more compressor horsepower, which means condensers and vessels and pumps and so on.
By the way, for the clarification of RACandH: please indicate whether this system is Recirculated or Gravity flooded...neither arrangement will benefit from subcooling but depending on the coil performance, it may very well benefit from liquid inductors.
