We needn’t even have a secondary token if implemented at the pool level: A percentage of the pool fee can be redistributed to loyal miners similarly to a PPLNS model, but over a longer period of time.
The redistribution could even be tied in some way to the difficulty adjustment, specifically rewarding loyal miners when the difficulty increases for a sustained period of time. See discussion here.
If a pool implementation is combined with a native implementation, loyal miners can be rewarded with very smooth rewards
I really like your second and third solutions as they would enable more decentralized collateralized mining pools to be formed:
Solo miners could still participate and smooth out their rewards if we can create the right economic incentives and inverse disincentives for cheating (i.e. loans for joining collaterlized pools as a solo miner.)