I'm open to trying new things.... Add a cap here or there to make it better:
There are loads of capacitors in that picture, it's just that they're SMD's... and just HOW do you think "bigger caps" would make the Rev2 better sounding? Did you just open an OLD synth, visually notice the bigger capacitors and conclude they're responsible for the synths sound? It's generally not a good idea to "add a cap here or there", as these are intricately designed CIRCUITS. You do know many old synths get re-capped, for worn-out caps? With something as simple as a passive low- or highpass filter circuit, sure, you can change a cap or resistor to change the cutoff points, but most beyond that is no go for me... The Rev2, as many other newer synths, are designed to be STABLE and RELIABLE, DIGITALLY controlled expecting a proper circuit, and NOT "vintage" (in the sense of unstable and unreliable). If that's what you're after, get a vintage synth instead, or program the Rev2 to sound more vintage-y, there are several ways. Mine certainly doesn't sound "thin"...
https://somanytech.com/smd-capacitor-surface-mount-capacitor/Resistors, too, used to be a lot bigger, just have a look at old 70's synths... does that mean the resistors "sound better", just because they're BIGGER? No. They're still just resistors, just as capacitors are just capacitors. The actual size doesn't really matter, as long as they're spec'ed high enough to handle whatever is required for the circuit. The RIGHT value of Farads for the job, and a high enough Voltage-tolerance for the particular circuit (or they may explode, which you DON'T want). I've modded electrical fly-swatters into wasp-terminators with HUGE film capacitors that handle 2000V but still are only 470nF, only reason being that they're less likely to explode, as the output produced is about a million Volts or so, enough to explode a wasp, and the bang enough to make your heart jump. If you look at the chart linked above, there are SMD caps at 6800nF, and they're a LOT smaller than my 470nF's, like 1000x smaller. So size isn't necessarily an indicator of anything, especially not on modern synths that mostly operate at low voltages, with little risk of blowing capacitors. What difference would a "bigger" cap do? The output levels are ALREADY very HOT all through the Rev2 board.
If anything, "add a cap here or there", will likely just mess up the circuit and something will break sooner rather than later, without benefits. Unless you REALLY know what you're doing, like if you understand the full circuit of the Rev2, I'd strongly advice against trying to modify it. But hey, I'm no engineer either, though the fly-swatters I mod only cost $5, and the Rev2 is a bit more... Anyhow, good luck with those caps!