It is possible to have your clients multiple IPs for their NAT
connection. As the Router(Mikrotik) needs to decide which client
IP(i.e. 10.0.0.x) should go through which Public IP, you should have
your public IPs on you Mikrotik router.
Just change your current router(192.168.1.1) config to bridge mode and set a PPPOE client connection on you mikrotik to connect to your ISP and get IPs.
(You might need to add the IPs and Routes subsequently in your mikrotik router after PPPOE connection)
This way you can set 3 access lists in the Mikrotik firewall and then SNAT each access list to the correct public IP.
Of course you should add your client IPs to the correct access list either manually or automatically by a script within the mikrotik.
Access lists are to make it organize better, you can also set you Client IPs directly to source address
field of your nat rules.
It might be a good practice to have the PPPOE server(192.168.1.2) in bridge and have the mikrotik to act as PPPOE server as well.
this way you can avoid setting IPs in the NAT rule and just use interface names!