Hello Joe,
This is a good approach, however most of the time the limits are scalar or fixed and then it would be ideal to just display the limit [and color legend if possible] as the first column in a row .
Similar to how there is possibility to add a custom column with some labels etc, we should be allowed to add in that column the limit value via property show method.
The limit can be a property of the Metric KPI row.
In case the limit is not fixed but tied to a signal, we could show that signal range in the column to give idea of range of limit values ?
Another way to look at it this is imagine we have 10 KPIs to display, then using your proposed approach quickly make that table at least double in height, as each KPI will have at least one separate row for KPI threshold.