Jayco will not recommend any modifications, I can pretty much tell you that. I'm not familiar with that trailer so I don't know if 15's are possible or not. Our 17Z has the same size on it now, IMO 15's would be to tight in the wheel well.
As to the skids, you really don't "need" them, I would say if you remove them, to make sure you always have the rear stabs down before going inside. I think it's very unlikely to tip one of these, but I've seen cargo trailers do it, I would not want that happening to my 17Z and even then, not sure how much good the skids would do.
I don't have any experience with the sensors yet, that's still new to me.
2013 Starcraft Travel Star 229TB
2011 Jayco X17Z(traded in)
2010 Jayco Jay Series 1207(traded for the 17Z)
2011 Chevrolet Silverado 2500HD Z71 CC 6.0L/3.73
Reese "Pro Series" 800lb Trunnion WDH w/sway control