Bitcoin network does not have any direct incentive to run a full node. But it is healthy for the network to have more nodes securing it. Hence I was toying with the idea that how a bitcoin node can be incentivized without disturbing the existing bitcoin protocol.

It appears to me that sidechains can be used for this purpose. If bitcoin nodes can be equipped in a way so that it can perform as a gateway between bitcoin blockchain and an altcoin blockchain, i.e. validating the altcoin blockchain with bitcoin network with every bitcoin block found, then this concept might work. These nodes will be super node for the altcoin network, but normal for bitcoin network. Those altcoin blockchain or sidechains may incentivize the nodes, like it happen in PoS and in return can be secured by the huge hashing power of the bitcoin network. The altcoins, secured by the bitcoin network, may also help to solve the ~10 minutes delay of bitcoin confirmation.

As I am not an expert of the sidechain technology, I'd like to know from people with knowledge, whether an altcoin blockchain can be pegged to a bitcoin blockchain using a common node ?