Locktime: you can set the locktime on your transaction so that it can only be included starting from the block N + 1 where N is the current block height. This way your transaction can't be included in a block with the current block height.

Reorgs: now I don't get you at all. I conjecture there might be confusion of reorg as in 51% attack scenario with greedy miner reorg (no 51% power). In the latter case the miner gets the coinbase reward anyway, so why does the coinbase size even matter?