How far can we push Miss Fortune's Passive before she's OP?

While not typically one of the first passives that come to mind when thinking of "Bad passives" as Ashe and Rene tend to be on the forefronts of those discussions, Miss Fortune's isn't exactly anything to write home about. Mobis as a passive, awesome. Awhile back they buffed it to stack up faster and it got me thinking of how far we can push this sort of passive before it's actually an issue.

What if strut just never broke and went like +20/45/75 MS at 1/11/16? What if she always had +70 regardless of circumstance? What if she only lost half her movement speed when damaged rather than all of it? What if she had bonus damage while strutting?

I'm not saying Miss Fortune needs buffs, just mostly musing over the possibilities. I liked to play the buxom bounty hunter but recently people have been complaining about the pick despite doing well most of the time, so maybe minor tweaks are in order? I dunno, all of her kit feels fine, except her passive. That's not really new, but hey, no harm in starting a discussion huh?