Auditable encrypted ledger
For all non-negative integers $n_0$,$n_1$,$n_2$ and random strings $r_0,r_1,r_2$

$n_0 \:\: = \:\: (n_0+n_1+n_2)-(n_1+n_2)$
$=$
$\operatorname{plaintextsum}(\operatorname{encrypt}(n_0,r_0),\operatorname{encrypt}(n_1,r_1),\operatorname{encrypt}(n_2,r_2))$

$- \: \operatorname{plaintextsum}(\operatorname{encrypt}(n_1,r_1),\operatorname{encrypt}(n_2,r_2))$

.

Therefore any such scheme would be completely insecure

if more than 2 non-negative integers are encrypted with it.