"equalable", "equalizable", or none of them?

This is one of those words you imagine might exist but probably doesn't – and if it does, it will be too obscure to use or have a default meaning other than the one you want. However, according to Merriam-Webster

equatable adjective: capable of being equated

different but equatable terminologies — Ethel Albert

and we surely need the appropriate sense of equate:

equate ... transitive verb

1a: to make equal : EQUALIZE

[M-W]

The fact that this is listed first by M-W is encouraging, but that could be because it is the most transparent sense rather than the most common. And even if the 'make equal' sense is the most common, this does not mean that 'equatable' might not have the default meaning 'that can be regarded/shown/treated as equivalent'.

'Equalisable', and as mentioned in a comment 'equilibratable', are sometimes found, but it seems more usual to find workarounds.