There's a bottleneck at Piccadilly and through the city centre. They could send more trams and line up as many as they want, you'd still end up queuing to get into Piccadilly, you'd just be sat on a tram going nowhere instead. The solution needs to send supporters in a different direction.
City won't spend loads of money on new track just for 25-30 days a year of use as it stands at the moment, and the council/tfgm won't pay for it while it works (I assume) for 340 days a year. The cheapest route I can think of would be to run a line from Asda up ATW, right onto Oldham Road and left into Central Park. A distance of 1.6miles but opens up trams to Rochdale and possibly Bury (if they are able to run "football specials" via the Engineering works at Queens Rd). Phase 1 Metrolink cost around £6million per km based on 2004 prices, so we're looking at possibly upto £30million I reckon for a really short route. When there's more happening at the collar site, then maybe a share of the cost between City and the council/tfgm could be considered.