Forget about the MS-20.
The MS-20 lacks VCO outputs, the patch panel is laid out like a circuit diagram rather than being associated with relevant knobs/functions, the filter doesn't track to the keyboard by default (which sort of defeats the purpose of a semi
-modular), and while the filter is unique it isn't a necessity (unlike, for example, the "Moog" ladder filter). These issues combine to make the MS-20 a poor choice for a 'first modular/semi-modular synth' in my opinion.
I have my doubts that Korg would release the Mini MS-20 anyhow, either as an analogue or digital recreation, because even if the issues I listed above are resolved its appeal is fairly limited for a large company like Korg. There's a few additions/modifications the MS-20 needs to broaden its appeal, and those changes are clearly not present in the mock-ups of the Mini MS-20 I have seen. For a company like Korg, the Mini MS-20 as it is seems like a weak product to me.
Having said that... personally I'd recommend you take a look the following as for your "first" semi-modular synthesizers:
01. MFB Kraftzwerg
02. MFB Microzwerge II
03. Tom Oberheim SEM Pro
04. MEM PALette v2
05. Mr. Acid Machine Agent C
06. Analogue Solutions Telemark-K
There was a new semi-modular listed on Matrix Synth in the last month as well, that piqued my interest, but I haven't got the link handy. I recall that one of the envelopes could be used as an LFO or oscillator, and that it featured some sort of waveform skewing. It's also worth mentioning that, depending on the gear you currently own, you may be able to have some of it modified to provide semi-modular functions.