1R to do BGP, 1R for tunneling (VPN s-t-s, VPLS, any other)

I would like to ask the community for help with this idea:

I wish to connect to an Internet Exchange Point IXP with this general idea in mind:
I would like to have a way to deploy vpn site-to-site, VPLS or any other tunnel against a ROUTER connected to an IXP. This router routes tunnel traffic from-and-to other BGP routers connected to IXP.
I get 2 mikrotik routers CCR1036-8G-2S+EM, ROUTER A, and ROUTER B.

The scenario is the following:

[] IXP switch connect to ROUTER A using SPF+. ROUTER A uses BGP to communicate with other routers connected to IXP-switch.
[
] ROUTER A is connected to ROUTER B, and ROUTER B is configured for tunnels.

So, from any point in internet, I want to be able to setup a tunnel against ROUTER B, and exchange traffic with other IXP networks. The strange (for me) thing is that the same connection, IXP switch - ROUTER A - ROUTER B) is used for in and out-bound traffic. Can this be achieved with MikroTik routers? I am planning on using 2 devices, to separate BGP and TUNNEL functionality.

Any recommendation, suggestions, comments?

I am planing this because I have no other means to do BGP against IXP routers from any point in internet.
Thanks!