No.
Integrating more birds take extra space.
A coop large enough for the number of birds you want would be the best way to go.
A second coop would get you to having 2 flocks, because they' all want to be in the same coop eventually.
Get thru this winter with the 3 you have, it's going to be...
Do not put more birds in that set up.
Do cover the sides of run leaving a gap at tops for ventilation.
Is the run roof solid?
If not, cover it to keep snow out.