Claude Matthews could be a good choice, but an even better one could be Ohio Senator Calvin S. Brice. He was sure to lose his seat in his upcoming 1896 re-election Senate bid due to Republican control of the state legislature, so it is not like the Democrats are losing anything by nominating him. He was a solid Bourbonite, and a Midwesterner to boot, so he would do well in balancing the ticket.
Brice had alienated far too many Populist Democrats during his time as Senator for his nomination to be tenable.
John McLean (D-OH) would be a better choice in terms of someone who is from Ohio who could also self-fund the ticket, but this was complicated by his ownership of the Washington Gaslight Company and his seeming promotion of monopolistic practices. Supposedly McLean took his name out of contention on the basis that the Democratic ticket should be a "poor man's ticket", but given how Populists reacted to Sewall's nomination I'm not certain they would have taken McLean's nomination any worse.
Joseph Sibley (D-PA) was also a popular name, but his nomination would have represented as clear a break with the Bourbon Democrats as could be made, Sibley having essentially made his career to that point ragging on the Cleveland Administration.
George F. Williams (D-MA) was initially a Dark Horse in the running, being one of the only Northeastern Delegates who had abandoned their pledge to a Gold Plank and endorsed Bryan for the Presidency. There was some hope among his supporters that naming him to the ticket would enable Bryan to compete in New York and New England, a handful expecting that Massachusetts might be competitive. His support was extremely soft however as seen by his decline from (76) to (16) votes over the first two ballots.