Well, as our little sucubus friend here was Carlos' first character on his original comic, it was just a matter of time untill he turned her into the main character, with or without having planned it. But I agree with zack, The priest should show around some time, and the Butler even more. Also, it would be nice to know how she ended up living with Leth, and who the hell is zombers.
It was planned
If you visit his deviant art, he has one picture of Giselle from before this comic started, and in the author's comments section he mentions that she is going to be the main character in a new comic he is making.
I'm not certain of the post date for that pic, but Carlos's previous comic before this and after the original Lowroad was titled "Giselle". He prolly gets hung up on her story arcs since they involve tets more often (No Complaint!). So yeeeeer.