This makes a great deal of sense. If you focus exclusively on one waza for this length of time you are going to absorb it into your muscle memory and it is going to become second nature when you deploy it in keiko or shiai.
The only word of warning is that you need to practice the technique correctly. Constantly repeating a mistake will only magnify it, so you need to be fairly certain that you understand exactly what you are doing before you commit yourself to 3000 repetitions per day.
The best way to improve is through kihon drills, but it is difficult to focus these exclusively on your own needs. In most dojo the training exercises are prescribed by an instructor whose job is to build a training programme that is valuable to everyone in the dojo. Often though if you tell your sensei what you are trying to do, he will set aside some practice time to help you, and you will have the bonus of him helping you get it right. I sometimes use motodachi-geiko sessions with students to work exclusively on the points that they are struggling with.
If sensei is not able to, or available to help, then it may be worth going to the dojo early with a buddy and working together on one technique, or taking turns to act as a target for different waza that you each need to work on. I know a number of people who have gone to the trouble of renting squash courts so they can spend some quality time developing their tokui waza.
What takes more discipline is to use your time in jigeiko to focus on one particular technique. Going into a keiko with the intention of only hitting men is commendable, but if all of your opponents are head and shoulders taller than you, it is difficult not to switch to dou of kote. Perhaps a better way is to set a goal of trying a particular technique a given number of times with each partner. There is of course a strong likelihood that everyone will catch on to you plan and make it more difficult for you to achieve your aim, but that resistance can also be used to improve.