Tell me you're joking right? do you really think changing POW is like changing a kitchen knife?
In order for such drastic change miners which are currently mining the POW algo will have to vote for the change of POW.
You can't go ask the president for example to sign a bill which will eventually lead to a new law that says we no longer need a president.
bad analogy
pools are not the president.
here is a better analogy
pools are more like a secretary that just collates data of the employee's and customers and has to file it in a certain way that regional bosses can read and accept
the nodes are the regional bosses they set the rules and read the secretaries work and sign off on if its acceptable or not. the bosses syncing up as a network to ensur they all have the same documents to hand that are all acceptable.
the secretary can type up chapter of files as fast as she likes.. but if the bosses/nodes dont like it. in the reject/orphan pile it ends up.
devs are the employee's they can make new product that the bosses may choose to adopt. but the bosses can still say nay/abstain.
devs are the employee's they can make new product and try to by pass the bosses and try getting the secretary to use the new products hoping it forces the bosses to change their mind..
but the secretary(pools) would still prefer to only do things the bosses(nodes) would accept. after all it affects the secretaries income(reward) if the bosses reject her work.
having many regional managers (diverse nodes) avoids a dictatorship
having many secretaries (diverse pools) avoids network delays if one pool(secretary) fouls up (offsick, resigns, makes mistakes, intentionally frauds the books)
having many employees (diverse dev teams) avoids devs going on strike or dictating what direction a company should move in. because the bosses can choose to avoid certain employee's idea's and find whats best for the company.
imagine the company as the symbiotic peer network.. there is no CEO .. just lots of regional managers(nodes) that ask many secretaries to give them a report of customer data(block of tx's) every ~10 minutes. the fastest secretary that sends the regional managers a good collection of data gets a reward
now..
to sack all the secretaries is not a soft decision. it requires the bosses(nodes) having to change who what and how the company(network) data is collated and distributed.
if this kind of event were to happen where the whole retail chain network has to change.. they might aswell use that opportunity to do the other stuff customers and employee's can all unite around too, which will make the (network) better for all.. rather than just sack the secretary because 65% of secretaries wont collate data in a way only one team of employee's from one region want.
You are over-complicating/confusing things.
Nodes and miners are one and the same.
You think if majority of nodes start a new protocol then miners will sit back and allow it? some one invested enough money to be a miner in the first place will spend more to have enough nodes to avoid the majority take over.
You say diversification of node versions while we all know that all the results across the entire network must be identical otherwise not accepted.
Lets have 50 different versions, they will all have to follow only one rule and that is the Bitcoin's code, and as we know running a program on different platforms is much harder and requires more work to be done just like when you have a software which can be executed in Linux/Windows/Mac but for a developer is much easier to just compile it to run on Windows, regardless it's still the same software only runs in different OS systems and that's a feature which makes the software available for all kinds of people.
In Bitcoin's case it's something else, if you are trying to run the node on any platform you are free to do so but what is your goal to run different versions of a software in the same network with same internet ports and same brand name?
How could anyone change POW without the majority of hash power support/vote?
Why would miners vote for something that makes their mining machines useless?
If I have 1
BTC no matter the versions of nodes I still have my coin sitting in my address, devs and miners should notice this fact that end user doesn't really care about those stuff what we care is when we send a transaction with a normal fee it gets confirmed after 30 minutes no matter what.
10 hours ago I sent some bitcoins to an exchange to buy some cheap alts but now while my transaction is pending and there are 150K unconfirmed TX I have lost a perfect opportunity. I don't want that, so what other choice do I really have besides moving to another alt?
Moreover we have diversification already but that seems not the issue with you rather you want both, you can't have heads and tails in one side of the coin.