Naramon spoiler ability is recommended for keeping your melee combo going, since that's the whole point of the build. For your Riven, in the case of this build, you definitely want Crit Chance and some kind of positive Combo modifier, be it initial combo or duration or w/e. Mine came with the added bonus of a boost to Slash damage which synergizes very well both with the KP and with the [Sovereign Outcast] stance (several of the attacks give a 25% boost to Slash).

PPP is pretty standard, obviously. CO does not really have a place in a hybrid build like this.

Berserker is gonna give these tonfa a pretty big speed boost, pretty consistently, especially when it's super-charged by [Blood Rush] and the Riven. AOS means you're gonna be able to detonate your heavy attack on a big boy without losing too much time, then Berserker and company are gonna come back to make up for the combo you expended.

Meanwhile, [Weeping Wounds] helps you with status procs (which the KP are already pretty damn good at for their class). You could probably go with two 60/60 Elemental mods if you want, I just like that little bit of extra damage especially given the attack speed and all those multihits and procs in [Sovereign Outcast].

Speaking of which, I went with Viral over Corrosive because I've been told that's actually better up until you hit extremely high-level armor values (which is funny because that's all I ever seem to see people run tests on) - however, since I'm not a guy who crunches numbers on this stuff, I'm not going to endorse that personally and if you replace it with Corrosive you'll probably be fine anyway.

One thing you may find lacking with the [Kronen Prime] which this build does not address is Range. I'm not sure you'd be able to mod a set of tonfa to a place where you're happy with that stat and still be able to match this damage output (possibly a different Riven), but I hope that if this build is unsatisfactory for any reason then it can at least help give some ideas for how you can try to accomplish what you want.

Also, doesn't it feel nice not having any wasted mod space?