Incidentally, a “partially succinct” block chain would not need to deprecate transparent addresses. It would be succinct wrt shielded transactions, so that blocks would only need to contain transparent transactions. That would be sufficient to solve the scalability problem — for example, if you freeze the transparent UTXO set and require further transfers from t-addresses to be shielding, then you have a bound on the total future size of the transparent part of the chain state. Even if you don’t freeze the UTXO set immediately, you’ve essentially reduced the scalability problem to discouraging use of transparent transactions in favour of shielded ones, which is a problem you had anyway.
In the case of Zcash, we’d also want to allow non-succinct shielded Sprout and Sapling transactions, but this doesn’t present any further obstacle. It would be also possible to allow shielded Sapling->succinct transfers, subject to concerns about monetary base auditing. One way to do this (potentially disruptive, but elegant) is to automatically convert all Sapling note commitments to initial account states.
(Note that discussing these ideas in the public domain essentially prevents them from being patented. ZcashCo hasn’t applied for any patents, and I’m not aware of O(1) Labs, the developers of Coda, having done so.)