Ezra's lightsaber is practical and innovative, the design isn't totally alien: during the golden pirate era (early 1700s), they actually invented a sword-pistol, look it up. Let's look at all the reason why he decided to build the saberblaster:
1. The era of SW Rebels restricts anyone from carrying or owning a saber, if caught you'll most likely be targeted as Jedi (which in the Empire's eyes, you are a criminal; kill on sight). Hell, even Kanan keeps his saber in two pieces so they won't suspect he is a Jedi. This is also the reason why Jedi in this time don't wear robes, it's called being incognito. Ezra's lightsaber is very discreet, yeah it's not elegant, it's utilitarian; I wouldn't call the Galactic civil war a "civilized age", so guess what? TIMES HAVE CHANGED!
2. Although he's 15 (barely), Ezra is still a kid, he thinks like a kid, talks like a kid, and acts like kid, don't get me wrong Ezra is a great character. SO when he built his saber he wasn't going for "beauty", "practicality", most likely, he was thinking about what was innovated and useful for the time.
3. He had limited resources, unlike most Jedi Ezra didn't have a Jedi star cruiser full of Lightsaber parts specially meant for young Jedi to build a saber like it how it's suppose to be. He had scraps! A focusing crystal from Yoda, spare lightsaber parts from Kanan, other parts from Sabine (probably parts to build the blaster), and a power cell donated by Chopper.
Personally I like his saber for what it was made for, AND Ezra has proved in recent episodes that he is VERY skilled with it...VERY skilled. He's probably now capable of fighting an Inquisitor by himself! Both Kanan and Zeb were impressed when he took out several stormtrooper AND agent Callous effortlessly, so it proves that it is an effective weapon.