If you become stuck on a rep for a period of time, cheating *can* be one of the tools (tricks) used to stimulate growth to get past that point, most make the mistake of adding sets.
For example the barbell curl; swinging the weight up using momentum, then very slowly lowering (6sec) continue until you are unable to control the lowering.
What is the issue you have with adding sets? If you perform the exercises with the cadences and controlled eccentrics as you prescribed, an extra set = extra volume which can be a good thing right? It follows the time under tension concept.
On the same token one could use the pause-rest principle instead if they want to keep it all within the same set. Or pyramid down the weights with minimal rest. All these techniques require 'extra sets', so taking that out of the equation completely is missing out on a fair bit of gainz, dontcha reckon?
For me, I would look at a method that would give me what I need by adding to, rather than robbing me from what I already have.
For example, performing / focusing on the eccentric phase of a particular exercise might really add to the effort of that exercise, but at the same time I feel robbed due to the way eccentric affect my ability to recover. So even though this style of lifting does work, my job would be to look for a method that would maximize my benefits whilst simultaneously minimizing any negative effect overall.
Performing extra sets would add volume to the overall workout, which is great, but it won't do, and here's my reason why that is. Adding volume to a workout is adding volume to a workout, in other words, it's way too general in its overall effect to solve a particular issue I happen to be suffering from, which in this case is a plateau in my strength level.
Enter the isometric/heavy partial rep movements here. performed in the power rack. Here is where weak links are not only eliminated, but are turned into one's strength, giving the lifter an overall balance throughout the lift. Furthermore, one needs to keep in mind that our focus here ought to be on intensity over and above effort. Where intensity is used to quantify the amount of weight being lifted, and effort is used to quantify the level of exertion during exercise.