I'm not quite seeing the downsides other people are seeing with this.
1. Zizzo was the 9th pick in our draft, hardly a top asset. Zizzo was also projected as a bench player even for NYCFC. Had NYCFC put this in terms of "We've given up our 9th pick in the draft to get a player on loan" I don't think people would be as angry.
2. Meara's salary is about 70k, which is 50k less than MacMath's last year. That's 50k more in cap room to play with.
3. The situation with Philly hasn't gotten better. Philly is still stuck with 3 GKs eating up cap space, one a DP! Moreover, their leverage sucks. Not only do teams know they have to get rid of them, as time goes on other teams will be looking to sell a GK (i.e. Orlando. Thanks for that Ricketts pick!), driving prices lower.
4. RBNY turned down 300k in allocation money for this. You want to get the better of them? Take meara, show the wonders of NYCFC, including actual playing time, shiny CFG facilities (and connections to Europe, a big thing for the man with an Irish passport), etc. Make it so after next year, he's demanding a trade. Suddenly, RBNY are in a worse bargaining position than this time, with one less year on the contract and an unhappy player. If you make good use of that time, you might drive down the price. If he doesn't like NYCFC, well guess what you saved 300,000 in allocation money for the price of Zizzo offset by a year of services.