Problem with date & data linking

Hello everyone!

I'm trying to build a model where I present different kinds of data over time, and I would like to be able to put all kinds of data on the same timeline. First of all, I want to create a stacked column + line graph like below.

Now, I have multiple rows for capacity, which all have different initial capacities. In addition, I have dates when improvements are made (then the capacity is 0 for a while) and then greater than initial capacities.
The need for capacity (line in the graph) comes from a different table.
I tried creating a "master date table", and with a following measure i got it to work - given that i set the source of the capacity (n001, n002,..) as a legend.

if(FIRSTDATE(Capacities[Improvement start date])>FIRSTDATE('Date'[date]),sum(Capacities[Initial capacity]),if(FIRSTDATE(Capacities[Improvement end date])>FIRSTDATE('Date'[date]),0,sum(Capacities[New capacity])))

Of cource, it doesn't work without the legend, because it always checks the first date. However, in the future, I would like to present the type of capacity, not the source of it, so I'll need it fixed. Any ideas how to do it?

Thanks!