Paypal has their technology, and Square has Venmo and their technology.
Paypal has a market cap over $40 billion, and Square’s market cap is close to $4 Billion.
If Paypal takes over Square, they can be a force to be reckoned with because of their economies of scope from secure payments to money transfers across friends, small businesses, large firms and businesses, e-commerce, etc.
Then, some big credit card companies such as Visa or MasterCard should buy out this Paypal-Square company and merge their technologies to create even greater economies of scope overall.
(Or, Yahoo could just sell its stake in Alibaba and use that money, along with maybe a stock swap or taking out a bank loan, to buy out Paypal and build up its e-commerce business to become a relevant company again).
Start from there!