I was thinking short square ballusters from Fypon so that the total height is 26" or 28". That matches some old farmhouses I've found in the area. The ballusters are pretty close together, too--closer than required by code. Is that what you had in mind when you said "a very low one?" Again, we might choose to leave the railing system off altogether, which would be my preference--on less thing to screw up. If we do add railing, it will be the last thing we do on the house at the very end.
I know what you mean by Greco-Roman balusters. For our 8" square HB&G PermaCast columns, our builder pointed at the "Tuscan" cap and base in the catalog. I knew it didn't look right. To me, it looked too "colonial" I said, but in hindsight I think it was what you meant by "Greco-Roman." It just doesn't fit. The old farmhouses I've found that have large square columns have a simple moulding at the top, kind of like a crown moulding, with just a flat cap and a cove moulding underneath. Then the base is just 1x6 clad around the bottom.
- John