Indeed, you only have to look at any Ham design combining multiple PA modules to see that! Why reinvent the wheel?
For mine, I calculated the line dimensions and modelled it with QUCS (free software), then I EM Modelled it in the box with Sonnet lite (free software)
Drew the final PCB dimensions from Sonnet in to Eagle 5 (free software)
Laser printed two of them on Press N peel on a free sample of Rogers board from the Rodgers website
Both worked first time!
Charlie G3WDG did a design for a 6cm hybrid as well but clearly tolerances get tighter the higher you go. Doing that so easily at 10GHz might be a bigger challenge but there are plenty of designs around for that band and even some for for 24GHz using microstrip hybrids!
Finally If anyone comes across an Ionica output combiner (look on my website under projects)
I show how you can easily hack the 3.5GHz hybrid down on to 3.4GHz with some Kapton tape.