The proposal to expand this unlocking idea to land is fine with me but I don't have a strong opinion on that matter.
The one big thing I don't like about this proposal is the section about combining manifested and non-manifested bcx as this would likely carry over to transferable cards later on:
Not being able to combine cards being made transferable and those that haven't. If, say, after the current soulbouds go out of print and I happen to be one bcx short (say 399/400) for some common card, I do have to bail out all 399 to be able to add one transferable bcx that I acquired on the market? This level-up then costs not only the market price for 1 bcx, but also 3990 DEC on top - for a card that I only want to use for myself anyways.
Is it not possible or not feasible to keep track of the fractions and any card that contains any number of souldbound bcx is considered soulbound until the difference is paid? Say Common Lvl 10, 400/400bcx, 1/400 unlocked. If I want to make the combined card transferable I have to burn DEC to unlock the remaining 399bcx.
Otherwise this will be a huge turn-off for people who just want to complete their collection by adding a few missing bcx from the market here and there.
So I would rather see effort being made to implement a tracker/counter for unlocked/locked bcx in a combined multi-bcx card then to figure out some confusing weird way to make them available for land now and then unlock them a second time for the market later. Especially since that complicates keeping track of locked/unlocked bcx by adding another level of "unlocked", which is probably why you specifically mention it in this proposal post.