Explain to me how the interaction of Switcharoo targeting my Shadow Clone with Assault 4 has with an enemy unit with 7 might.

Yes — it fully swaps the numbers: your clone becomes 7 Might and the enemy drops to 4, with Assault staying on the clone as part of that value.

While attacking, the clone's current Might is 0 (base) + 4 (Assault) = 4. Switcheroo snapshots current Mights (4 vs 7), finds a difference of 3, and applies +3 to your clone and −3 to the enemy. Assault is not reapplied on top of the new value — it was included in the snapshot and keeps applying to its original unit (FAQ #341, same as the Assault/Shield Switcheroo precedent). So during combat: clone = 0 + 4 (Assault) + 3 = 7, enemy = 7 − 3 = 4.

Consequences: the clone deals 7 combat damage (lethal against the 4-Might enemy), while the enemy deals only 4 back — not lethal against the clone's 7. After combat ends, the clone loses Assault and drops to 3 Might (0 base + the +3 modifier, which persists until end of turn). One edge case: if you cast Switcheroo while the clone isn't attacking, its Might is 0, so the clone would gain +7 (enemy drops to 0) — and if it attacks later that turn, Assault 4 stacks on top for a total of 11.