You could write a plugin im sure.. At start of layout do the required for steam. But yeah that would require a little work but no you could get it to work. Many indies can see success without the need of steam. Steam is nice and all but you could do good with out it.
On a side note offtopic and kinda on topic.. ModDB is releasing a new digital distribution service that is coming out in april. Maybe you could see if there is any success there with your title as well under the idea of self publishing.
You can sell a game in construct, just you need to put forth your own work towards it. And some options may not be available off the bat but you could possibly get something out there from other indie sources and review sites like
that can get you out there and you could self publish also. These are just some options if you look into it you could find a lot of ways to self publish and make a living.