The roof is plenty strong to do as you please within reason and if weight is properly distributed. I have toyed with the idea of a rooftop deck but to make it safe it would require significant time and effort. the 2 main things with an Eagle roof is 1) anytime walking up there be cautious of the seams to avoid leaks. If you put foot pressure just before or aft of a seam it could pop the factory adhesive. 2) if you plan on a roof top deck, engineer it with little to no holes if possible, again to avoid leaks. Mine would utilize 3M VHB Double Sided Foam Adhesive Tape 5952 (100% coverage) and a large fillet of siaflex on each side of square tubing. I would run about 4 rows of square aluminum tube rails the length of the coach at four parallel uniformly spaced locations keeping the weight evenly distributed. I would only recommend doing a rooftop deck if it is clear of anything other than the tank vent or maybe a satellite dish (meaning basement air over rooftop). Again, weight distribution is key.
Regardless of the use, Before you do anything, I would scrub it clean, wire brush the seams, fillet seal the seams with sikaflex, repaint (I used KM Industrial paint from Kelly Moore). Remove and replace every light if possible, again resealing them with a fillet of sika. When we had gutted our '93, EVERY roof hole had leaked at one time or another (southern run coach) and I would imagine as good of shape as ours was in, this would be true with most all Eagles. Also check out amesresearch.com. I used their 6" tape over every seam on ours after the sika application. Just my opinion for what its worth...Hope this helps.