In books of Bengali Wikisource, Bengali numbers are used as page numbers. For front matter pages, similar to roman numerals, Bengali currency numerals are used in old books.
Example having both types: https://bn.wikisource.org/wiki/নির্ঘণ্ট:গৌড়রাজমালা.djvu
So provision of these two types of numeral system is required for pagelist creation.
General Bengali numerals follow a decimal system ("0123456789" = "০১২৩৪৫৬৭৮৯") and thus adding support for "beng" numerals from the ICU, similarly to how the change from T268906 allows use of "thai" numerals, would suffice for this.
Bengali currency numerals, on the other hand, follow a hexadecimal system as follows:
i=৴৹
ii=৵৹
iii=৶৹
iv=৷৹
v=৷৴৹
vi=৷৵৹
vii=৷৶৹
viii=৷৷৹
ix=৷৷৴৹
x=৷৷৵৹
xi=৷৷৶৹
xii=৸৹
xiii=৸৴৹
xiv=৸৵৹
xv=৸৶৹
xvi=১৲
(Note how xvi uses the regular Bengali numeral "১" with the currency zero placeholder "৲".) The values from xvii-xxxii follow a similar pattern to the above with a prefix "১", except that xxxii will use a prefix "২" instead of a prefix "১". All values higher than xv are thus effectively written by rendering the number divided by 16 without remainder in regular Bengali numerals, rendering the number modulo 16 in currency numerals, and concatenating the two (so that clxviii becomes ১০৷৷৹). A custom ruleset à la those from https://github.com/unicode-org/cldr/blob/master/common/rbnf/root.xml will likely be necessary for this.