Multi-mono version of those plug-ins are certainly not intentionally missing. Since those effects tend to be stereo out in nature, we just never did mono out stems of them. However your request makes a lot of sense and I'll add it as a feature request for a future update.
In the meantime the work around will have to be what you are doing now, down mixing those stereo stems to mono, or just using 1 channel of each stereo output and setting your pans correctly.
Thanks for the feedback and good luck with the plugs, let us know if there is anything else we can do for yo.