But it IS true that VMCA is "set" in the sense that once determined for a give alt/temp, it is then applied for all instances of that temp/alt. That is, heavy aircraft must use the VMC(A/G) applicable to a light aircraft; you can't schedule with aircraft weight.
MINIMUM VR
Altitude: Sea Level and below
OAT WEIGHT (kg)
(°C) 24000 26000 28000 30000 32000 34000 36000 38000
10 98 96 95 95 96 96 96 97
15 98 95 95 95 95 96 96 96
20 98 95 95 95 95 96 96 96
25 98 95 95 95 95 96 96 96
30 98 95 95 95 95 95 96 96
35 94 92 92 92 93 93 93 94
40 90 89 90 90 90 90 91 91
45 87 87 87 87 87 88 88 88
50 84 84 84 84 85 85 85 86
From an AOM near me.
Although it's min VR in this manual in the FAA version the tables are VMCA and a knot or two lower.
So it looks like you can factor weight into the mix.