If it did, a side benefit would be that, at some point, a Ryde to Newport DMU or battery MU service could be considered.
Best put the crayons away.
The IoWSR is unlikely to get much closer to Newport - closest it will get is around the Cross Lane area which is a mile outside Newport town centre. And Ryde St Johns is a fair distance out of Ryde town centre.
No DMUs have ever operated on the island, so there would be all the cost of getting a unit there, staff training etc.
Retaining the 3rd rail makes it VERY unlikely the IoWSR will get to St Johns in any case.
The quickest bus between Ryde & Newport takes 35 mins - the train is unlikely to be any quicker.
Lastly, only 1 heritage railway has managed to run a regular 'non tourist' service - Swanage - and that has a park & ride next to it and is to alleviate traffic and parking problems at Swanage - that's not an issue in the same way for the IoW.