If you have an Arduino Bit, you can give DieterVDW's modulator a go. http://littlebits.cc/projects/arduino-lfo-adsr
However, you will need a gate converter to run the ADSR and other bits like the oscillator bit and envelope bit properly at the same time, and it just so happens that I worked on this over the weekend.
Essentially, the OSOM solves all issues related to using modulations that aren't standard to the littleBits system.
When ti comes to other filter types, it is already possible to get them by combining splits, filters, inverters, and mixers. You will want one split, one inverter, one mixer, and two filters to get started making your own filter shapes. You can get every shape from a classic SEM filter using those parts.
I will probably get an MS20 mini when they drop even lower in price. However, the freedom to make my own modulations with Arduino bits is great. Not to mention that I could use these modulations with an MS20 via the cv bit.