In general nodes should not implement this type of restriction as it has the potential to affect the integrity of the network.
It is better than not having a node at all.
Even when throttled, the node will still forward blocks that are less than 30 days old and inform peers of the 2nd highest block that it knows about.
This means that peers will fall at most 1 block behind the chain if they only connected to the network through a throttled node.
An easier method is to have a script that shuts down your bitcoind "bitcoin-cli stop", once your specified bandwidth runs out. This way you can run a standard node without any degradation of service right up to the point where you simply turn it off.
What exactly is your concern? The worth case is that the node consumes one connection from a "full node". SPV clients already do that anyway and this node is actually mostly contributing (up to the bandwidth limit).