I think he would have His problem seemed to stem that Tony, who he still regarded as an inferior, was now the Street Boss/Acting Boss and he, who had just gotten out of the prison after 10 years, wasn't being "cared for" like he expected. I also think Richie was trying to milk his association as being the late boss's brother, which is clear by him shaking down Beansie Gaeta when he had no actual right to do it, and then him going against Tony because Tony wanted him to be patient.

RE: Junior's involvement, it's clear Junior would have backed Richie if Richie had gotten any support, but the problem is that a hothead like Richie would have been more trouble than it's worth. Could you imagine him as a boss? He was even more flagrant than Tony was; he did after all beat the shit out of Beansie in his pizzeria in front of a bunch of staff and customers like it was nothing at all, so as a boss he would have easily been nabbed on something because he would never be able to keep his temper at bay.