Now, in the abstract, yours is the more natural definition. But experimentally, it turns out to not give the best accuracy.
I believe one starts with (1) the meter (which is based on a second defined using a atomic transition, plus light) and (2) the Newton (which is the force required to accelerate the all-important kilogram at 1 meter per second squared). Then an Ampere is the amount of current flowing through two parallel wires required to produce a force of one Newton per meter between the wires.
http://en.wikipedia.org/wiki/File:SI_base_unit.svg
Now, in the abstract, yours is the more natural definition. But experimentally, it turns out to not give the best accuracy.
I believe one starts with (1) the meter (which is based on a second defined using a atomic transition, plus light) and (2) the Newton (which is the force required to accelerate the all-important kilogram at 1 meter per second squared). Then an Ampere is the amount of current flowing through two parallel wires required to produce a force of one Newton per meter between the wires.
http://en.wikipedia.org/wiki/Ampere#Definition
Now, the technology is apparently improving enough that it may be possible to actually count elementary charges like you suggest. See here:
http://en.wikipedia.org/wiki/Ampere#Proposed_future_definiti...