Don't see why it shouldn't work althoug I'd rather have a home-made version than a commercially produced one.
Brown bread ice-cream has been a traditional recipe for years and most recipes for ece-cream call for egg yolks, so all you need for French Toast flavoured is cinnamon. I may have to try it.
(But I promise not to base it on my favourite savoury FT variaton - celery salt and braised mushrooms on top

)