How to synthesize and isolate single stranded cDNA from an RNA template?
Sure that will work, or gel purify the ss cDNA, or treat the rxn with alkali to degrade RNA.  The real questions in my mind are:


What will you use as a primer for the RT?
What are you going to do with this pure ss cDNA?


If you already have the target cloned (how else would you transcribe it in vitro?), then why not just do a linear PCR where you cut the plasmid to linearize it at the site of your choosing, and then throw it in a PCR machine with just one primer?

Why bother going through the T7 RNA pol and RT steps (if you don't need to)?