if you think that is what holds up the BTC network then you guys know less than I thought. 90% of the network (likely more) is major mining firms and ASIC manufacturers testing their new products until they are no longer profitable. Perhaps the first year that was true, but they weren't "tom dick and harry" they were people in the technological "know" that knew this was something game changing. THAT is what holds up the BTC network, my friend
The point isn't whether they're kids in their bedrooms or exotic mining firms. The point is that they are all uncontrolled third parties. ALL crypto currency networks are maintained by uncontrolled third parties - that's inherent in the term "decentralised".
I think what you're trying to say in a kind of roundabout way is that there is less redundancy in a heterogeneous network than a homogeneous one. That is certainly true but it isn't a showstopper, particularly when that heterogeneity is supporting a network-specific service.
I think it all depends on the implementation. It might be a weakness, on the other hand it might be very bullet proof. Look at the myriad of client-server or peer-to-peer applications on the internet that are very stable despite being "operated" under a wide range of hosting environments and end users.
I don't know enough about the master node implementation to know what its strengths and weaknesses are - I suspect you don't either. But the software should be robust enough to tolerate "what if they dont know enough about security?" and "what if they just plain stop giving a shit?" scenarios 100 times over just like any critical network software should be.
At any rate, we're soon going to find out because it's going live in a week so you'll be able to observe it in action.