Just do a tourney with 50% of the starting stack of your main same blind structure. Super simple.
This doesn't automatically achieve the goals of the OP. What you proposed will roughly make the tourney time the same as the main tourney minus about two levels (depending on the structure of course, but it's quite common for the blinds to roughly double every 2 levels) if the chip count is the same (big if).
12-16 players, let's say 14. Perhaps 40% rebuys given that it might get a bit splashy? That's about 20 buy-ins.
Here's an example using base T25 and 200 BBs. 10k stacks means 200000 in play, should end when the BB is about 10k.
BB (where SB of course is half)
50
100
150
200
300
(Color up T25)
400
600
800
1200
1600
(Color-up T100)
2k
3k
(Color-up T500)
4k
6k
8k - should end about here
12k - or here
16k - sometimes nits are heads up and it'll end here
20k
Etc
That's 15-16 levels with 2 10 minute breaks and one 5 minute (coloring off T500 is fast). 3h minus breaks is 155 minutes. 155 divided by 15 or 16 is about 10 minutes per level.
Beware though, that short levels might lead to splashy play meaning more rebuys -> longer tourney. Also, short levels often mean that tourneys don't end when planned since there isn't enough time to knock everyone out, so don't be surprised if it lasts longer.
