Allow me to disagree about the difficulty of a turn based game. The state of who's turn it is can be represented in a variable. Then use the variable compare condition in events to control when things happen. That is pretty much the main aspect that makes it turn based.
After that you can tackle each other aspect individually. The computer AI will be the most difficult but is doable.
Oh, the basics are simple. I had a basic version of the battle system of loot pursuit running very quickly when I first started on it years ago when I didn't know what I was doing that seemed to work just fine at the time. It's all the extra layers of the rest of the stuff that's not basic working with all the other tons of systems together smoothly that becomes a very complex problem if you don't know what you're doing from the start, one that I would not recommend for someone starting out with construct (though it did end up being quite an effective learning experience for learning how to use construct for me). RPG's in particular at first seem simple to make, but are extremely deceptive with how complex they end up being.
Also, you are one of the top level programmers around here, so what's easy for you, as I'm sure you're aware, might not be easy for someone else. :)
I'm inclined to agree with R0J0hound on the ease of developing a turn based game... for someone who knows how to work with Construct.
I still maintain that even with experience, anything past the most basic of RPGs is going to be a much more complex task than it seems. I feel confident stating this objectively as I have read many other people agreeing to the same thing who have attempted making RPGs.