Matt - it’s nice to have for sure, but not necessary. Anti-spark itself isn’t truly needed (it reduces wear on contacts and electrical surge to ESC). So you can skip to start, or go simple w/ an XT-90 anti spark loop key:
Or go w/ the full push button anti spark from Enertion/DIYes and others.
Like others - i’d recommend the GT2b (only ~$25!) - and put in a smaller case later (badwolf, mad monkey, baby buffalo, etc.).
Single motor setup - 12 or 15mm wide. 9mm is tough to keep tight enough to avoid skipping when braking hard (like avoiding someone who isn’t paying attention). I’d get a set of gears w/ belts from DIYes or Enertion.
83mm Abecs - perfect. exactly my preferred starting point. Larger is great for rough roads, but 83 is about the best all-around and starting point IMO.
VESC - you won’t be disappointed. Just be careful to start and stick to the 60k ERPM limit to avoid DRV issues. I’d also start out BLDC and wait for FOC (or v6 VESC) to be more mature. YMMV.
Batteries - if you are going VESC, i might suggest thinner batteries in series like 3s packs - then you can do 6/9s for slow/fast setups (great to give a friend 6s to avoid hurting themselves on test-ride). Less expensive and i like the lower profile option. Personal preference so no biggie either way.
Charger - Check out the SkyRC iMax b6ACv2. All-in-one vs a charger and ACtoDC power supply. Not as fast as an iCharger (206/306), since it maxes at 5/6A vs 20/30a of iCharger - but simpler and still has features like Internal Resistance test and a great reputation as a good charger IMO. I have iCharger 306 and Dell server power supplies for 24v 1500W… but not really needed 99% of the time for a slow charge to ride the next day… And slower charge (like .5 C) = longer pack life which is nice too. In a rush to ride after work - it’s nice to have ability to do 5C (as an example - each pack will have max C rating) charging - but tough on the pack and you need something “beefier” than the B6ACv2.
HTH - GL!