Bladesinger "Boost" I'm Thinking of Implementing.

Hi everyone, before you say anything, yes, i know that Bladesinger is already very powerful and versatile. But i think it needs a small cleanup on one thing that i saw became problematic. Quick context, i'm a forever DM who tends to play with various different people who have never played the game before but wants to give it a try, this "Boost" is basically something that i observed from a good amount of them.

The problem is the infamous "Setup Round", activating "Conjure Minor Elementals" with your action and "Bladesong" with bonus action. I've seen for a good amount of time that while new players (at least the ones around me) always gets intrigued with playing a "War Mage", but when they sit down to make a proper road map about their characters, this Setup Round almost always makes them play a different class. They don't like the idea of spending a round, we don't have much gamblers here i guess. So i came up with an additional feature, which i haven't started using yet. I'm going to explain the feature, my reasoning, and the pros/cons that i came up with and would like feedback from y'all.

Mythic Blade (Level 6 OR Level 10 Bladesinger Feature). When you activate Bladesong, you can also choose to conjure a powerful blade as part of the same bonus action by expending an at least level 3 spell slot. Mythic Blade deals 2d8 (Piercing, Slashing, Radiant, Necrotic, or Psychic. Your choice) damage on a hit. You must concentrate on the blade as if you're concentrating on a spell. Damage becomes 3d8 if you expend a level 5 or higher spell slot while conjuring the blade initially.

So what this does (or is planned to do anyway), is to erase that setup round with something not as powerful as CME, but is still powerful enough to be usable. The problem with CME is that while it's a gamble to use in this context, it shreds everything if it pays off. This is a less powerful alternative to CME, but with a much smaller risk and consequences. The upscale limit to me also prevents it from becoming an all-powerful feature. Anyway, thoughts?