This actually has all of the basics, although you might find it useful to look into a smaller LFO module. That Fonitronik is huge, and takes up room for some other modules that could push the build a lot further. 1 x 84 isn't much space, so shrinking things down as much as possible is important. Alternately, you could also look into a larger case if you've not acquired this one pictured yet. That would open up space for a couple of other VCOs (important for getting things to sound 'fatter'), maybe some waveshaping to dirty up the sound a bit, a few useful utilities such as mixers, mults, and the like, and also a few more VCAs to enable control over both audio and CV levels.
But as a base-level emulator for a 303...yeah, it's got that covered.