I agree.....that's exactly what people want. Nothing more - just the added function of enabling the custom palettes and borders is enough for a Game Boy emulator.
It's why even to this day I still prefer GB emulation on my DSi XL as GameYob displays games perfectly 1:1 with their corresponding SGB palettes and borders.
Game Boy emulation was most accurate on the gba. But the screen was just too small. So I prefer to use the DSiXL as well. Gameyob3DS or Gambette are not as good as the Lameboy or Gameyob on the NDS.
Oh well, one day I guess game boy emulation will be best on the 3ds though