Last but not least, what are the disadvantages of shorter blade bats? Will an inch or 1.5 inches make a dig difference?
No, I use them regularly. If you are catching the short balls on the top 1 inch of your bat, you need to adjust your technique.
Is it difficult to play defensive shots?
No. I hook and pull just fine with shorter blades as standard SH bats.
Is it a feeling of nakedness from lack of willow when you lift the bat to defend a short ball? I can't think of how the top of the blade would be used to defend but perhaps I'm not thinking of something?
These modern t-20 bats don't feel lacking during the defensive play. I have used shorter blades than that and was fine.