Here is a proposed new transaction format.
version_num, # Transaction format version, 0 for now
chain_id, # 1 for ETH, 3 for ropsten...
shard_id, # The ID of the shard the tx goes on
acct, # The account the tx enters through
gas, # Total gas supply
data # Tx data
Depending on what is done in Tradeoffs in Account Abstraction Proposals, fields can simply be added on to the end of this as needed.