OpenStreetMap's New Vector Tiles

The other issue is that the arabic font is not rendering correctly in the vector version. It's rendering left to right (instead of right to left) with characters broken up instead of linked.

The whole point of vector tiles is that the rendering is local and controlled by a style configuration (except for the tile schema) that can be changed. So the brokenness you are seeing is either in the style or the library that is rendering the contents locally.

Indeed, but that is probably not going to help end users of apps.

Well nobody claimed things are going to get simpler.

It is difficult to beat raster tiles in that respect. vector tiles split up responsibility for what you get visually over multiple moving pieces with different provenance and operators.

For Arabic specifically, different users want text to render differently, so you'd want to do it on the client if you can.

(Some countries use Roman numerals and some use Arabic numerals for numbers. And by Arabic numerals I don't mean 1-9.)

All Arabic-speaking countries use Arabic numerals. Some use Western Arabic numerals (123) and some use Eastern Arabic numerals (١٢٣).

Roman numerals are I, V, X, etc.