Having a Marketplace will not affect Scirra and it's development at all.
In fact I'm sure that if Ashley sees a thriving community buying and selling engines and graphics, he will be pleased. This will attract more potential early adopters.
Look, if somebody buys a template and hardly works on it, it will never end up for sale. So clones are nothing to worry about.
For serious developers, having an engine as a base makes total sense. I have no ego when it comes to game release. It's all a business to me. If I didn't code the element where a tower chooses to fire on the closest/weakest/strongest enemy then what does it matter?
Producing a game that looks great and is entertaining is my responsibility.
To all coders, set up Paypal for payment, code an engine for a game type (you don't even have to make any graphics, just functionality).
Then charge $10 or whatever. I guarantee you will make more money selling to us in here than you would releasing a game.
If admin could just open a new "Marketplace" topic in the Construct 2 Forum we can get going.
For those wishing to code the whole game on their own they need never click on that topic.
If you want to see the potential of this just go over to the Gamesalad forums.