we're aware that the current design isn't optimal and once we have time or a user submits a patch we'll change it such that each value has it's own table row.
using external tables with g2 can be problematic, at least i guess we'll much more likely redesign our current customfields implementation than offering a GUI to let g2 use external database tables.
of course you can do that for your installation, but it probably won't be on our development roadmap.
ps: please use the forum search function. this has been discussed before.