i like a coin that can solve completely the size of the blockchain by resume the blockchain from a previous more recent point without the need of pruning and with the possibility of using different wallet after you activate this not like pruning where you need to resync again, i also like faster confirmation but not with orpahn and more anonymous coin like zcash/zcoin
i have been tackling the first idea you mentioned. I tried running it on a testnet, but my idea is incomplete. So far online wallets have no trouble with the transition, but new wallets have trouble with syncing.
I'll highlight the problems
1) the new block created as a "balances checkpoint" must be dead accurate
2) How do we prevent a miner from manipulating balances in this block
-- Maybe have local machines audit the data ? or
-- Have the block only be produced with a special dev signing key ?
3) New wallets
they just start from the last "balances checkpoint"?
-- If so how do they ensure they are on the right chain ? Genesis block isn't enough, since attackers can create a fork just as long or even longer than active chain.
4) In case of catastrophic re-org / fork , what then ?