SRS is right. It is up to the operator to ensure that the airport has the correct category of fire service for the size of aircraft operated. The airport declares what category is available at any particular time. If the aircraft is too large for the category available, you divert or do not start engines.
If some of the fire staff go on strike then it is likely there will be a variable category declaration shift by shift. So when the shift change time arrives the category can change which might cause problems for the landing stream of aircraft - and those waiting to take off.
On security, the passenger search teams will either stop or delay passengers going airside in the terminal. Annoys the passengers but doesn't directly affect aircraft.
Access security manning the gates will affect departures as no security then no access. Most likely result will be managers manning one (or more) gate with consequent delays and queues.