I never thought that using tumble to stand back up as a free action should be that difficult either, and before thier even was a 'Kip Up' feat, and before the ELH came out I was letting characters with tumble do it as a DC 15 action. In fact, I was letting characters who where tripped or thrown stand back up as a free action _on the turn they were tripped_ (for instance to negate the +4 to hit improved trip's free attack would normally recieve) as a DC 25 action. Those numbers were based on a comparison of the difficulty in tumbling through an enemies square - a feat of skill that seemed far harder to me than either form of quick stand.
If someone wanted to take a narrow idea like 'Kip Up' as a feat IMC, I would probably translate it into giving them a +4 bonus on the above rolls, and allow them to take 10 regardless of circumstance. Effectively, this would let them Kip Up for free provided they had no huge penalties on thier tumble roll.
I've always liked tumble, balance, climb, and other skill checks and thus never felt the need to develop whole classes (like Duelist) to make a lightly armored combatant doable. A lightly armored combatant might not have quite the advantage in a straight up fight, but there are just sooooo many other situations where you would be so glad you aren't hulking around in 60 lbs of steel (as any real life adventurer should be able to attest).