Recommendations for WAN Aggregation and Gateway for Small (16-24 server) Data Center Setup

I am setting up my equipment in the datacenter. Currently I have as follows:

• 16 compute nodes, which may expand to 24 in the near future
• 2 WAN networks; one provided by the datacenter (lower-ish bandwith) and another by a 3rd party telecom provider (1Gb connection)
• A LAN network amongst the compute nodes that needs to be segmented off from remainder of the network for reasons that aren't important here
• A LAN network amongst the compute nodes for basic internet access

The equipment that I possess is:

1. (2) Arista Switches (7124x) -- separate for each LAN
2. Ubiquiti Gear: the USG (considering upgrading this to a USG Pro or a Dream Machine Pro), and a Ubiquiti 24 port Gigabit Switch

The issue that arises is that both of my WAN connections arrive on SM Fiber only and thus require an SFP connection. My USG is Ethernet Only and supports WAN aggregation across two WANs. My 24 port Gb Switch has 2 SFP ports. Of course my Arista has 24 SFP / SFP+ ports.

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My question is: How do you recommend that I configure my WAN connections from the SM Fiber that the Datacenter provides me to the USG? And, do you recommend another product that would perform the role of the USG and would support SFP/SFP+ connections? Ubiquiti doesn't seem to provide such an option but it would be nice to stay within the same product line there since I'm not building out a 500 node datacenter installation just yet.

I have considered:

• Datacenter SM Fiber WAN => Arista [n] => Arista [n+1] => USG WAN, where the Arista [n] and Arista [n+1] ports are on a dedicated VLAN.
  
• Datacenter SM Fiber WAN => Ubiquiti 24 port Switch SFP => Ethernet port to USG WAN. In this case, I may be able to make the SFP and the Ethernet port on the Ubiquiti part of a VLAN but I need to confirm this is possible.
• Purchase some new equipment that would replace the USG and have two WAN SFP connections.

Any help is appreciated.