I am not sure which if any coins used in the Galactic Milieu are up to date enough with bitcoin code to work properly with the various methods folks have come up with for doing cross-chain atomic exchange. For example I think a lot of them still have "malleable transactions" even as they are so old.
So what you're saying is that bitcoin code has updated beyond where our coins that began on blockchain and froze when you began issuing tokens for them on your Digitalis Open Transactions server using Open Transactions have transaction malleability issues since most of the Galactic Milieu coins inspired by BiTCoin probably never fixed those issues one can read here:
https://en.bitcoin.it/wiki/Transaction_malleability... I can see how using a blockchain such as Bitcoin's with former blockchain coins that have been locked up in your custodial possession might not exactly be compatible when writing and signing transactions for blockchain coins across two invalidating blockchains...
Open Transactions planned to federate the reserve-custodian function but I had to move on from that platform as they refused to finalize data formats or warrant that there would be conversion tools to migrate data from old to new formats if/when formats changed.
So currently acting as custodian of the coins represented by tokens still seems somewhat necessary for various of the coins.
Keeping coins for now as a custodian while allowing people to trade tokens with other tokens on a platform such as Horizon or Stellar DEX is a temporary and easy solution to avoid issues with the actual blockchain coins and their possible incompatibility with Bitcoin as its network and BIPs have changed the rules to invalidate compatibility with older blockchain based coins. Data could even be incompatible between Berkley DB 4.7 and 4.8 and any Bitcoin/updated Bitcoin codebase chains that have since moved to other databases that are not backward compatible with the one my Devcoin - Wallet uses (Berkeley 4.8.30 April 9, 2010). So not just malleability issues there I assume, but things beyond my head that would tend to make me agree with you about atomic cross-chain transactions between our ancients and the current Bitcoin and it's blockchain/transaction/software parameters. Token swapping in a DEX like Stellar or on a self-run server and platform where these tokens are backed, or migrated from DOTs and Open Transactions to the Horizon Platform "home" and bridging with OTC transactions work for now. Clearly I've never had any complaints with you. But we do need to modernize soon. Unless it comes to us instead.
But hey if you can somehow figure out which if any of our blockchains will work with whatever cross-chain stuff your system does to secure coins on the real blockchain that are in use as tokens on your system I'd love to hear which ones should work and see it implemented.
Since your big seven Galactic currencies began as coins, fully issued 21-million in supply, and migrated rather quickly to Open Transactions and your methods of tokenization/custodial control of coins, those blockchains were last edited testnet configurations within a bitcoin client if I am not mistaken? With Merge Mining, its clear DVC coins and their raw blocks directly copying "Bitcoin block - transactions (really)" already sort of are compatible. But to call it cross-chain I would say to me it looks like layers that work well keeping a record with a DVC coin transaction on top and a copy of a raw Bitcoin block tx beneath on the "raw Devcoin block"... Sort of like printing on both sides of a sheet of paper with information that goes quite well together. I have never personally examined a GRouPcoin block but I am aware you said that too was stripped and reverted back to 50 coins per block indefinitely, that it is on a blockchain still, and that it was a test run to see if what you planned for DeVCoin and it being secured by POW merge mining would work. So there's another blockchain I've never looked at, but perhaps one in combination with our other merge mined chains (I0Coin being merge mind but 90 second blocks, IXCoin having a blockchain with big blocks and being an original sidechain to Bitcoin, etc).
Next platform Galactic Milieu is likely to issue onto is Diamond (DMD) when its "version 4" comes out. Meanwhile accumulation of DMD in readiness for that era is ongoing.
-MarkM-
By no means am I an expert at atomic swapping but I do believe that IXCoin, I0Coin, and others have fixed malleability issues in recent updates. Devcoin appears to be right where it needs to be (maybe the addition of other milieu configurations could help with any rate limiting necessary for secure swapping), and finally - automation. How does that all happen without a custodian, with real coins, and blockchains? Maybe we use our own unique and secure blockchains of the Galactic Milieu, the platforms and their legers as well as their unique features like HORIZON's DAE and POS/Leasing, Stellar's token swapping, but with automated ways for us to issue tokens while proving we have the coin to back them, and like you've planned, perhaps one more meaningful migration to DMD version 4 - when it becomes a platform that you believe will work for us. And if the bottleneck is still speed to pull of such transactions lets just use cross-platform/OS configuration mods like the first GG/GEG Geist Geld and it's Multicoin-exp fork
A good wallet, but one you can only access your coins out of and per the rules set forth by the protocol. Uniswap muniswap.
These are just a lot of ideas. But I'm sure you know better than I what I'm getting at. I'm a fan. Keep it up! But definitely use our blockchains if we got some to spare without coins generation/transactions with coins but room for other data on them. Cough HORIZON cough