Using speed of polymeraze to sequence DNA?

[Jarek Duda]

There are considered some approaches to sequence DNA base by base - for example by making it go through nanoscale hole and measure its electric properties using some nanoelectrodes.
Unfortunately even theoretical simulations says that identifying bases this way is already extremely difficult ...
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Maybe we could use nature's ways to read/work with DNA?
For example somehow mount polymerase or ribosome and somehow monitor its state...

I thought about using speed of process to get information about currently processed base.
For example DNA polymerase to process succeeding base has to get from environment corresponding nucleoside triphosphat - there are only four of them - we can manipulate their concentrations.
If we would choose different concentrations for them, there would be correlations between type of the base and time of its processing - by watching such many processes we could determine the sequence.

Is it doable?
What do you think about such 'base by base' sequencing methods?
How to use proteins developed by nature for this process?