Not as bad as it sounds to set up tbh.
I have 4 osc in my case and 3 filters, they’re all pretty different, so it depends really on what sounds you feel your missing from the A4 palette.
Current OSC:
Intellijel Shapeshifter - Crazy dual digital oscillator, can do FM, wavetables, wavefolding and more. Great sound, only just got this one.
Intellijel Rubicon - Analog Thru Zero Fm beast, very precise sounding with lots of inputs and outputs, probably want at least another oscillator though to get the most out of it.
Mutable Instruments Braids - Digital multi function oscillator, can be many different things.
TipTop Z3000 - Analog flavoured beast, got a great raw and rude sounding saw wave and the sync sound on it is great too.
Of the four I’d say the Shapeshifter is probably the most interesting and different from the A4/AK sound but I like em all for different reasons.
Current Filtes:
Toppobrillo Multifilter - really nice multi output filter, so can output lp, bp, hp and notch at the same time, with a mixer you can mix the results to get different shapes (really good if you have a bi-polar mixer)
Synthesis Technology E440 - Really creamy old school LP filter, based on the Seq Circ Prophet topology. Has outs at different curves, again a bipolar mixer can allow you to get different shapes.
Malekko Borg 2 - Weird one this, really screamy resonance, can be lp, bp or notch. Uses vactrols for filter response, so it doesn’t snap to values like the other two. Can sound organic.
I did have a Doepfer A124 Wasp filter at one point, that is mental really odd, breaks up and goes nuts as you approach self oscillation.