I hadn't thought of your ideas and it actually quite answers a few questions that had yet formed in my head (between work and 4 kids I often lack time to reflect on anything else!). If as you say JA liked these novels herself, then we really can look at her defense of novels in Chp 5 as her true feelings, where I had thought that perhaps JA was saying it in jest. It makes a great deal of sense to me now.

I like the idea that the Tilney's can allow themselves the enjoy these novels, but are steeped in reality.

I can't help but to think that JA is also parodying the gothic novels, there are just so many similarities that Reeba has pointed out!