About the Ancient weapons, we know one can be made(there can exist many at once also) and one can be born(so many will exist just not at the same time) to finish of the puzzle i wld say the last weapon is one that has always been there(will probably always exist so no new versions or such), so i dont believe a man can b Uranus and that Uranus is something akin to the physical manifestation of a God's Ether so whoever has it can do shit as they wish with the power of the heavens. Oh and last vague assumption is that I think u need to take it in to you similar to a df but not quite it wld b like something u breath in or it phases into u or such, basically i d say its the precognator of df's(they are fashioned after the uranus system).
That said I think its impossible to have uranus and a df at once(gut feeling like everything else) but coz uranus is like having the spirit of a God in u and not a devil so unless u want your body to be the actual Apocalypse battle ground u dont experiment. As for Dragon i d think if he doesnt have it he has a lead on its whereabouts unless its in Raftel and someone codenamed it one piece(if thats the case then that no df and uranus sync is a load of crap as most thot upon 1st read).
Strength wise I d say he right up there with the Top of the summit pple though i expect he will die before op concludes as a death of the chief that spurs the troops on to get the victory kinda tribute(really though its so Luffy can stand as the protagonist in the final war). Sometimes guys who start or revolutions don't live thru to see them successful its usually the followers that inherit the dream that see it fulfilled(sorry to any Dragon fans but hey now u know how it feels when the say Mihawk and Shanks will bite the dust for me 'it's all good its for the story' he said trying to reassure himself a tear sparkling in his eye.)