Enquiry as to support status of multihomed support

[daemon]

Good day,

At present I have three residential internet connections, 2 PPPoE(vdsl2) and 1 LTE/4G, all are around the same speed. with the main differences being the LTE connection is more latent but has slightly higher bandwidth up, the 2 PPPoE's likewise have less latency.

I have it configured as of right now on my router that the 4G/LTE is an emergency line, and the two PPPoE's are split between domestic and office stuff (meetings etc).

What I would like to do however is combine the bandwidth of all three lines and and then route my connection via one of my servers. Somewhat:

/->Line 1->VPN-\
Router->Line 2->VPN->Server -> Single connection
\->Line 3->VPN-/

So a single get request from a computer on my lan behind my router would be able to download at a file at around 3 times the speed, obviously it would be more like 2.5* due to protocol overhead.

Would softether be able to cope with such a setup?

For further note, both the router on my side and my server are freebsd, though I could swap them to linux if it would be neccesary