Seems to me that these are at odds. If you're open source, why does anyone have to pay for these things?
If you're open core, I think it's mighty misleading to say things like "We will always be open source" because then not only is it untrue on its face, but also if someone contributes useful features to the open source project that compete with or supplant your paid proprietary bits, you are incentivized to refuse to merge their work - extremely not in the spirit of open source.
My perspective, which you asked for, is that open core is dishonest, and that you should be honest with yourselves about being a proprietary software vendor if that's indeed your plan, and stop with the open source posturing.
If I've misunderstood you, then I apologize.