I do exactly the same, oven in the winter, grill in the summer but while I make excellent pizza that way the recovery time between pies is a problem. I usually do 4 or 5 pizza’s at a time & also use two stones but the second (sometimes third) round takes much longer which drags the whole process out. A smaller dedicated oven takes a little longer to heat up but only has a few minutes recovery time between pies, also it frees up the home oven to hold the other pizza’s while I make the new ones so we all sit down to eat at the same time. It’s really all about using the correct tool for the job, no different than me having a dedicated smoker, griddle & Summit to fill in the gaps.