There is no morally plausible and defensible justification of the Lockean Proviso. Exclusive ownership is the result of real-life irreversibility. The first has the advantage of excess information, has invested work, time, effort. The act of owning involves investments and the latter relate to the future. By taking on investment risk - the first owner attains ownership.
Ownership is the compensation for investment risk, setting the asymmetry straight.
Profits reflect inherent inefficiency, an intrinsic compensation. There is a law of conservation of benefits, the situation is always win-lose. If we say, on the other hand, that ownership is the result of adding value to the world, of improving reality - it is only reasonable to expect it to equal all the value added which can be derived presently and in the future. But these are phenomena of the past.