We do this in our league, as it got boring or "vetteling" but we do it on a gentlemans agreement - anyone caught not doing the required 2 compound races forfeits a race.
But as we have the new tyre compounds, currently trialing out which compounds are best for each track.
For 2 compounds to work, the IGP developers need to add a push level setting when configuring the stint as doing 2 compounds becomes boring once people figure what push level to use for each track / temperature and tyres - we found this out in our 14th season.