my second D2 Pad's digitizer got cracked and the device useless. for anyone getting a cheapie i do recommend a case, or light touching, which can be hard in the latter as some of them have lousy touch response or resistive screens.
there is hardly any chance a custom ROM will exist, for the hardware as these are not favored by devs who put more time making ROMs to work with more popular brands like the Galaxy S or Nexus 4. both are far more capable. the cheapies have undersized RAM so i wouldn't think that running Jelly Bean AOKP would be pretty in 512MB RAM and a single core CPU. also, for custom ROMs to install you need a custom recovery such as TWRP or CWM, both requiring the build for your hardware, and without this you're sunk even if a ROM existed.
if one truly wants to run something like CyanogenMod 10 on a single core, 512MB cheap tablet, i suppose it may be doable, if you like having the performance of a Pentium 2 running Windows XP Pro