If I understand what you are trying to do, I'll tell what I'd do.
If I'm correct, ports 1-5 and 6-10 can be connected as a switch.
What I'd do is:
- set up ether1 the master port for ether2-5.
- set up ether6 the master port for ether7-10.
Now, you will only "see" traffic counting through ethernets 1 and 6 because they are the only ports connected "directly" to RouterOS, but all ports are working, don't worry. Using the switch features you will offload CPU the task of managing a huge 10-port bridge.
- create a bridge and add ether1, and ether6 to it. Set up RTSP to avoid Layer2 loops.
- Add your "internal" IP (...140.1) to the bridge1 (or ether1 or ether6).
- Add your "external" IP (....70.132) to ether11, 12 or 13.
Now you are done.
Connect the rest of your equipment to ether1-10 taking careful account of what IPs you are assigning to them (if you assign them statically). The default gateway for the rest of the equipment is ...140.1
But, I'd prefer to split the full range in two /25 (or in four /26) ranges and assign each half to a different sectors of the network. Splitting in two /25 is easy to understand: you can assign each half to each switch and assign a gateway IP to each master port.
But don't alter your plans if you are not sure about how to mess with subnetworks. You will learn about it (the hard or soft way, it depends on the problems you find).
There are too many variants to network segmentation to explain them here but knowing the basics, knowing your plans and thinking in future expansions you will find a good solution that works for your network and for you.
Good luck with your network.
PS: You are a lucky for owning a RB1100; they are hard to find.