It takes longer to shuffle the deck than to play a game of Blackjack. Like Odraude said, any role-playing challenge will usually feature one, maybe two characters, and often will take a few minutes at least. The snark of "do you make your players play lawn darts?" is also pretty insulting. You're in the homebrew section. And you know, if I worked with my players and we decided to make a game that combined lawn darts and rolling for ranged weapon attacks, that's well within our rights.
I'm not making anyone do anything. I asked my players if they'd want to try out a system I made, they said "Sure!" enthusiastically, because I've made things like this in the past that have turned out to be fun additions. We played it, they enjoyed it, and we're keeping it. Being the member of the Paizo community that I am, I decided to share it in case someone (like Odraude) would want to use the system or could glean inspiration from it.
Thanks for checking in though.
You're perception of insult and snark is not what I intended. I made those statements to illustrate a point. The point that you are removing the point of character investment (or at least heavily trivializing it). I'm not telling you to not make up house rules to make the game more fun, but I was telling you my opinion of your game, which was that I would hate it because my character investment means next to nothing.
Now, if you wanted to modify your system....
I would suggest that for every 5 of the skill modifier you give the player an additional hand to play against the dealer hand, and requiring only one hand to beat or meet the dealer hand to succeed. This makes skill investment more meaningful. I would also add that for every 5 in the skill you can add or remove 1 point to any hand. Such that, at a 20 you could add or remove 4 to any hand you have.
I like the idea of adding a benefit at "X amount of ranks" though I think having the extra hands would begin to slow down the mini game a bit. Also I think five might be too long of a wait for setting the investment pay off. Three or four seems like a good fit. Hell I'd even go with every two levels, you get a boon to your skill, if only because I like interesting mechanics to make skill challenges more fun. Increasing the range is the obvious go-to, since it is simple and requires little math. I could see the disabler gaining points based on Disable Device ranks that allow a redraw or add/subtract points to the total.
Only thing I do wonder is how one differentiates the DCs of the traps if you are using skill ranks instead of rolls with this method? Would harder traps and locks have lower values to match with blackjack?