Sure, Mica. My theories on midrange come from experience with various preamps and variations on their recommended settings. I find that, especially in live situations, a boost around 200-250 Hz with the right shape does wonders for fingerstyle punch coming through. I use that for Motown and Blues type stuff and I prefer the tone it creates above what I get from boosting deeper bass frequencies. This may be a matter of practicality since the power and speaker area required to do a solid job with low bass is more than the typical bar-band gigger carries.
The other range I find useful for more jazzy clarity is the area around 750-850 Hz. I use this a lot less since I don't focus on that musical style as much.
The third midrange setting that might be useful to a slapper is the auto-smiley-face-creator. I don't do that, so I couldn't say what it should look like.
I would like to have had a midrange control in my custom. I would have liked an internal pot to dial in the frequency and either a three way switch or a cut/boost knob to set the gain. If it were hard-configured, I would go for (flat/+6 @ 250/+6 @ 750) in a three-way toggle. I never cut mids in my style of play.
As a general mod, a quick tone switch tied to an internal frequency-setting pot would be the most flexible. That way, Rogue electronics would just have two identical switches with the frequencies pre-set appropriately. The owner would then be able to set those two switches however they please.
Thanks, Mica!