People don't see it as 5 Spider-man movies, they see the original 3 and then the terrible 2 reboot movies with that British guy (talk about not giving people more credit for intelligence). A new Spider-man would be another reboot, if not an origin story, especially if it's 2099 Spider-man. I don't think that people are tired of PP, just the Spider-man character. After the first couple movies, it became like any other superhero movie where the villain is the main character. A Hispanic PP would not help because it's still Spider-man vs "some enemy with cool powers that we haven't seen in live action movies before." So if Marvel wants to add Spider-man to the larger universe, there is no need to change the character, just give him a supporting role like Thor or the Hulk in Avengers.

What you're missing about the other characters is that Marvel released entire movies with these characters before including them in the larger Marvel universe. So what you're suggesting is that Spider-man 2099 get his own movie (which would do poorly) then be added to an ensemble movie. Or that he randomly appears in a Marvel universe movie, but he's from the future and the current day Spider-man is where exactly? Dead? Busy with school work?

Your comparison to the Terminator movies is redonkulous because that entire franchise is based on time traveling. Genetic mutations and technological advances that allow super-human powers doesn't make bending the laws of time and space a trivial matter. Oh, a guy can fly, next let's re-write all the laws of physics!