I have always had a few issues with how tech levels were presented in SM, but I can agree with making a simple system to explain and quantify a difficult discussion. But there are a few areas that still bother me.
1) Exploration TLs: Exploration is a natural (in most cultures) response to gaining an advance in transportation tech, and starts immediately once the tech becomes available. In other words, exploration is a result of a technical advance, not an advance in and of itself. To me these should be "X technology is refined, expanded, and becomes more available as the culture continues to use the X to explore."
2) trying to fill every tech level with an advance in the specific level charts. in some instances this spreads related advances across multiple TLs when they should be in one. It's OK to leave blanks or to have minor advances that will build into a group of major advances.
3) Progression. Relative power level of tech as one advances seems to be more of an exponential increase then a linear increase, which is what the table implies.
1 & 2 are easily dealt with, Here's my simple adjustment for 3.
Since all of the tech books use TLs it is impossible to separate them with out rewriting, so any changes have to work with the existing TL system. So, the way I have changed them is as follows.
TLs 1-10 are unchanged
TLs 11-20 have half TLs inserted
TLs 21-30 have quarter TLs inserted
If you feel that changing the interval to every 7 TLs you can. You can also adjust the increase, I use powers advancement (2, 4, 8, 16, etc.), but you could use additive or something else. You can even just add a decimal place to describe how far along a TL a culture is (5.3 vs 5.9, 29.0 vs 29.9)
This provides a little more granularity in describing TLs. And remember, the TLs are a guideline (which I admit to having problems remembering from time to time).