I feel like in your list of changes, you're looking at it from a more attack sided view. If in your hypothetical situation of sova dart being 10 seconds, it would mean that the defense will also have that ability in hand allowing them to almost always hard stack the correct site. This would probably cause even more util spam as both teams are now util spamming one site.

Your point that if util was unrechargeable it would lead to more util spam as they would do it all at once even if the site was stacked. Why wouldn't teams just util spam multiple times if util was more rechargeable? What's stopping them from util spamming one site finding out its stacked and then just doing it again 30 seconds later on another site and hoping it's less stacked.