There is probably no other way than to do it off-chain. I guess the transactions required to send your bitcoin to a wallet(if this feature will be enabled) might already be a problem. but this brings us to the entire bitcoin as a store of value idea, square will probably avoid the fees with bulk purchase of bitcoins. I have a big problem with that, bitcoin block rewards relative to the total value of bitcoin are going to decline over time. After the 2020 halving the block reward will be less than 2% the value of the network[1]. i assume satoshi imagined that overtime people will use transaction fees to secure the network. with bitcoin core moving to off chain solutions with no fees, i dont see how this will work out.

[1]http://www.bitcoinblockhalf.com/