I think getting a pack from a competent builder is a great idea.
For a commuter board you use for work, I would stay away from plastic gears. They’re not as robust as metal.
If you want to keep it light, then only build a vehicle that goes about twice as far as you need it to. Using a grossly oversized battery will kill your dreams of it being light. As a battery ages, its capacity can degrade a little bit. Also, keeping the battery current turned down can help range, longevity, and reliability. 20A battery current per motor is really plenty and it can have a high range and be very reliable, using parts that other users run far more power through.
Also order of operations can help you greatly.