That is certainly thinking on the bright side.If you think about it, what were Natalie's chances of ever experiencing a dungeon in her life? With this, she can forever boast about how she was stranded right in the middle of one and survived.
My guess is that the loss of his friend might have broken something in the old man, hence why he doesn't seem actively hostile to anyone. And I agree that he is looking for something, but I don't think it is to bring his friend back, but maybe something to remember him by, or he had a keepsake of the friend that he lost in a dungeon, so he keeps making dungeons to try and find the item again.So I guess the pensioner is creating dungeons to find something special. Probably involves a sob story that involves someone similar to Hajime, who he probably lost due to some tragic accident and what not. Now he keeps seeking that something to regain what he has lost and also being the wacky wizard that he is, he also transforms any place interesting into a dungeon for shits and giggles too.
I predict the guild master will end up kicking his ass in this arc.
Just stick with it a little longer. It is a slice of life manga that is focusing on an adventurer, so there are going to be parts like this.this arc is kinda boring, events are random enough that i don't feel any 'stakes' or 'rules' and i'm not seeing any character development or anything. i have hope it will get better though