Some go even further - my daughter uses Makaton, which is a sign (and symbol) language designed for people that have difficulty communicating (for different reasons, including cognitive impairment and neurological problems). In general the idea is to only use as many signs as you need, although of course you can amend depending on who is communicating.

As a point of note, Makaton is used at least a little at a lot of primary schools in Scotland (I would guess across the rest of the UK too), as a "supplementary language" for all kids.

[0] https://en.m.wikipedia.org/wiki/Makaton