Octet

Say this first

By business impact, and the result should be two or three standard branch tiers, not a custom design per site. A small office gets one edge device and one circuit with LTE backup. A medium site gets two circuits from different carriers on one device. A critical site gets two edge devices, two diverse circuits and a redundant switch stack. Multiplying each tier's cost by the number of sites keeps the conversation honest.

Go deeper

Tier	Edge	Transport	LAN	Typical site
1	One device	One broadband or fiber circuit plus LTE backup	One switch	Small sales office
2	One device	Two circuits, different carriers	Small stack	Normal office
3	Two devices	Two diverse circuits, LTE as third	Stack or pair, dual uplinks	Plant, warehouse, store with critical systems

Questions that decide the tier

What does an hour of outage at this site cost? Can staff work offline?
Are there local systems (point of sale, production lines, cameras) that need the WAN?
What can the carriers actually deliver at that address? Sometimes only one fiber provider exists.

Design details

Real diversity: two carriers can share the same last-mile duct. Ask for the path, not just a second circuit ID.
SD-WAN: measures loss, latency and jitter on every path and steers applications to the path that meets their policy, so two internet links can replace an MPLS circuit for many sites.
Two edge devices: need a first hop redundancy protocol (VRRP or HSRP) or routing on the LAN side, and each device owns one circuit.
LTE: watch data caps and costs; consider sending only critical traffic over it.

They will ask next

Is LTE a good primary link for a branch?
It can be for temporary or very small sites, but latency and throughput vary with signal and cell load, and data plans can be costly. As a backup it is excellent because it shares almost no physical path with a fixed circuit.

Traps

Giving every branch tier 3 because it is safest. Multiply it by the number of sites before proposing it.

How did you do?