my 10 project :)
I think that 1st and musthave partnership for NEM - it's ANKR. They are providing node supporting for users. And you can start you node there with 1 click. I used it to run Harmony node and i liked their servise.
Other partnerships - i think it would be grate to have some with Defi giants like Maker, Compound, REN or Aave. For example Maker already creating one more project - Venus on BSC ( binance smart chain ) it would be great if something similar would be on Symbol in future. For examle Maker can create DAI on Symbol. Or REN could start mint their renBTC using Symbol blockchain.
Also you can try to work with KEEP Network project. They are also have created tBTC( almost like renBTC ) it's wraped BTC on Ethereum.
You can make partnership with Orion Protocol. They are making agregator for all Defi platforms. they are working with DEXs and also with centralized exchanges also.
I think NEM and Symbol should be used in many wallets, For examle you Should be represented in Trust Wallet or Math Wallet. I think it's mandatory. also Trust wallet currently runing many their own Marketing programs and i think they will also be happy for new partnerships. For example it would be big news if you could create Opt-in possible in some other wallets, that will support both NEM and Symbol blockchains. For now most popular wallets is Trust, Math, and Atomic. Btw Atomic wallet already supports XEM so it would be much more easy to work with them. But in any way i think that NEM and Symbol must be suported by Trust Wallet.
I also think you should find some project that are working with cross-chain swaps. At the first stages launching Symbol we need to attract ETH eco-system to Symbol some how. And to do that - we need cross-chain swaps. Something similar that already doing Acala project for PolkaDOT eco-system.
We need our own swap Platform on Symbol blockchain. that will work the same as UniSwap on ETH or PanCakeSwap on BinanceSmartChain. So maybe you should to try make partnership with guys from PanCakeSwap to make them work with Symbol :)
So i think this is my full list of 10 projects that you should try to work with )