I'll get started by saying I think fastest map is balanced.
However, I would like to see a 4 player fastest map or 6 player map.
There is a couple of problems on fastest map.
1. Mid left or mid right base while your opponent is above you.
To top it all off! He's going to turtle and play super defensive and rush nukes/guardians/carriers/drops/tanks.
2. Build order loss. ZvP. Let's say the Z is scouting, P scouting as well. They don't know each others races (P is 4 gating). Z is unlucky to scout the P 4gating hand P is able to break the Zergs choke or do a lot run by.
Let's be honest. How many times have a Zerg player lost because of late scouts on both players.
It's like pick your poison. Hurry up and sunken hard with a few zerglings. (Blindly) Or be greedy and get your fourth hatch (including main and choke) after your first sunken.
If I've made my case and didn't bore you, I would be willing to try (not change) a few different things on fastest map for an example...
1v1 Fastest map but on a smaller space.
4 player fastest map.
6 player fastest map (with out the mid left and mid right) while the top mid and bottom mid have a choke like the corner locations.
Or maybe keep the same 8 player format for fastest but the mid bases have the same corner choke. Maybe a bigger map. 192x192.
Also, I wouldn't mind seeing two mineral patches for each base, (one above the main, one below the main) technically, bottom base players can get an extra 8-32 minerals compared to players above them.
Last but not least! I would like to see a UMS UGL Fastest map in case people want to obs (and the players are okay with that) so when the game starts, the players don't need to vision or ally anyone, while the obs can have AC chat on with each other.
I'm happy with fastest as it is. I threw these ideas out there for some perspective on a different variation on fastest.