I've spent the past few weeks measuring various aspects of the stages, here are my results. All tests were done in Training mode on a lvl. 3 Mario set to "stop", and all measurements are rounded to the nearest half unit. Every testing method matched Battlefield's confirmed measurements.
1. Blast Zones
Method: Recorded kill % for Ganon's Jab (side) and full hop Dair (top) from the center of the stage, then went to the training room and measured how many units Mario flew at that %. Have not found a good way to test bottom blast zones yet.
Stage|Side Blast Zones|Top Blast Zone
Battlefield|22.5|18
Dreamland|23|18
Yoshi's Story|21|17
Fountain of Dreams|22.5|18
Midgar|23|18
Final Destination|22.5|17
Pictochat|21|17
Wily's Castle|23|19
Umbra Clock Tower|23.5|17
Smashville|22|17
Yoshi's Island|20.5|17
Wuhu Island|23|20
Pokemon Stadium 1|23.5|17
Pokemon Stadium 2|23.5|17
Unova Pokemon League|22.5|17.5
Brinstar|17|17
WarioWare|16|18
Lylat Cruise|21|16
Frigate Orpheon|21|17
Halberd Flying|22|17
Halberd Ship|22|16
Castle Siege|19|16
Town & City|22|18
Mushroom Kingdom U|23|19
Skyloft|21|18
Kalos Pokemon League|23|18
2. Stage Length
Method: Recorded kill % for Ganon's Jab from the edge of the stage, then went to the training room and recorded how many units Mario flew at that %, subtracted that number from the side blast zone and doubled it (center to edge is half the stage, so that x2 is full stage).
Stage|Length
Battlefield|15
Dreamland|14
Yoshi's Story|13
Fountain of Dreams|15
Midgar|16
Final Destination|15
Pictochat|16
Wily's Castle|18
Umbra Clock Tower|19
Smashville|14
Yoshi's Island|13
Wuhu Island|20
Pokemon Stadium 1|18
Pokemon Stadium 2|19
Unova Pokemon League|17
Brinstar|10
WarioWare|10
Lylat Cruise|14
Frigate Orpheon|10
Halberd Flying|16
Halberd Ship|19
Castle Siege|13
Town & City|18
Mushroom Kingdom U|19
Skyloft|17
Kalos Pokemon League|16
3. Platform Length
Method: Recorded kill % for Ganon's short hop sweetspot Fair at each edge of the platform, then went to the training room and recorded how many units Mario flew at that %, and subtracted the second number from the first.
Stage|Side/Bottom platform length|Center/Top platform length
Battlefield|3|3
Dreamland|3|4
Yoshi's Story|4|4
Fountain of Dreams|3|3
Midgar|4|4
Smashville|0|4
Yoshi's Island|0|5.5
Wuhu Island|0|4
Pokemon Stadium 1|3|0
Pokemon Stadium 2|3|0
Unova Pokemon League|3|0
Brinstar|3, 3|3
WarioWare|3.5|2
Lylat Cruise|3|3
Frigate Orpheon|0|4
Halberd|0|5
Castle Siege|3|3
Town|4|4
City|4|0
Mushroom Kingdom U|5, 5|5
Skyloft|5|4
Kalos Pokemon League|3|0
Note: If there are two numbers listed in the bottom/side platform column, that means there are three platforms at different elevations. The second number is the middle platform.
4. Stage Height
Method: Recorded kill % for Ganon's full hop Dair from platform, then went to the training room and recorded how many units Mario flew at that %, and subtracted that number from the top blast zone.
Stage|Side/Bottom platform height|Center/Top platform height
Battlefield|2.5|4.5
Dreamland|2.5|4.5
Yoshi's Story|3|5.5
Fountain of Dreams|1.5-2.5*-3|4.5
Midgar|2.5|4.5
Smashville|0|2
Yoshi's Island|0|2.5
Wuhu Island|0|3
Pokemon Stadium 1|2.5|0
Pokemon Stadium 2|2.5|0
Unova Pokemon League|2.5|0
Brinstar|1.5, 2.5|3.5
WarioWare|1.5|4
Lylat Cruise|1.5|1.5
Frigate Orpheon|0|2.5
Halberd Flying|0|2.5
Halberd Ship|0|2
Castle Siege|1.5|2.5
Town|4|3*-6
City|3|0
Mushroom Kingdom U|2.5, 3.5|4.5
Skyloft|2.5-3|4.5
Kalos Pokemon League|0|3
Notes:
* If there are two numbers listed in the bottom/side platform column, that means there are three platforms at different elevations. The second number is the middle platform.
*If there's a range instead of just one number (ex. 1-2), that platform either moves vertically or is a slope. The number with the * next to it is the height with hazards off.
*These numbers are based off of the vertical distance from the center of the stage, not the part of the stage directly underneath.
5. Comparing Similar Stages
There are some stage archetypes that multiple different stages fall into. These are Battlefield-likes, Final Destination-likes, Smashville-likes, and Pokemon Stadium-likes. they're grouped together in the above charts, but I'll group them together again.
Battlefield-likes:
Stage|Side Blast Zones|Top Blast Zone|Length|Side/Bottom platform length|Center/Top platform length|Side/Bottom platform height|Center/Top platform height
Battlefield|22.5|18|15|3|3|2.5|4.5
Dreamland|23|18|14|3|4|2.5|4.5
Yoshi's Story|21|17|13|4|4|3|5.5
Fountain of Dreams|22.5|18|15|3|3|1.5-2.5*-3|4.5
Midgar|23|18|16|4|4|2.5|4.5|
Final Destination-likes:
Stage|Side Blast Zones|Top Blast Zone|Length
Final Destination|22.5|17|15
Pictochat|21|17|16
Wily's Castle|23|19|18
Umbra Clock Tower|23.5|17|19
Smashville-likes:
Stage|Side Blast Zones|Top Blast Zone|Length|Platform length|Platform height
Smashville|22|17|14|4|2
Yoshi's Island|20.5|17|13|5.5|2.5
Wuhu Island|23|20|20|4|3
Pokemon Stadium-likes:
Stage|Side Blast Zones|Top Blast Zone|Length|Platform length|Platform height
Pokemon Stadium 1|23.5|17|18|3|2.5
Pokemon Stadium 2|23.5|17|19|3|2.5
Unova Pokemon League|22.5|17.5|17|3|2.5