Sorry, man, but as @stragies guessed correctly, we deploy Mikrotik devices and even x86 hardware with plenty of RAM/Flash/hard disk space to do tasks as those you are talking about.
Our problem is not that we want to remain on 4/32 hardware out of homesickness, but that we really don't want to compel our people to buy new hardware, while what they already have at home can still be made to work fine.
So, we don't want to replace any user device unless absolutely necessary, but for newcomers we are willing to buy the newer, beefier, and even cheaper, hardware available today, that we know is working fine now, which was not the case when this thread started.
Again, my 2 cents: it is probably better for you to get a beefier device anyway
Please note I'm not saying you can't do, or shouldn't do, what you want. Probably you already have an old 4/32 device and simply want to try it out of curiosity. Anyway, please feel free to check -or build- what you want, and please let us know how it works.
And please note that you have plenty of snapshots for tiny devices here:
Last time I checked one of those it had IPv6 support, it was stable and it ran without any issues, as you asked for. Again, YMMV, so If you test any of these and find it lacks IPv6 support, it's not stable or is having issues, could you please report a bug, or, even better, post a patch?