Try it! Your ideas are sound and playing for a gimmick can be fun!
I’m about to start using a Fighter whose whole thing is shield bashing to shove enemies around and I expect it to be bad in most encounters.
I played a Ranger with Booming Blade and most of the time I didn’t use it, but when I did it was very satisfying.
A fighter using Booming Blade means not benefiting from its Extra Attacks. It’s nice at low level, but replacing 1 or 2 of your swings with some damage if you hit is situational. See this analysis. There are utility cantrips. For use in combat I’d pick a ranged damage spell and Mind Sliver is only Verbal so no need to free a hand up.
Like heating your kitchen by opening your fridge door. If it isn’t enough, add fridges!
He has no experiance in ever fighting anyone or anything.
Don’t forget your character should have a reason to be with the group and fit with them and go adventuring. Not knowing how to fight is commoner-levels of skills and will force rapid character progression from the start.
Mad Mage campaign, last night’s goal: walk from Skullport through Undermountain’s caves to River Sargauth’s gondola “service”.
Enter Azrok’s Hold, show papers.
Security is high, a patrol intercepts them, show papers.
Exit the Hold, ask for directions to the River, show papers.
Get ambushed by Azrok’s bugbears, show papers.
There’s a hobgoblin squad ahead with clear signs of a recent skirmish with drows, show papers. Yes, the River is that way, be careful of the drows.
After a bend in the caverns, they have clear line of sight to the River and proceed. Drow ambush.