[c-nsp] Access Switches Aggregation

[Robert Hass]

Hi
I'm looking for aggregation devices (access switches aggregation).
I need to aggregate around 170 access switches. Each switch need to be
connected to two core/aggregation devices using mLAG. There are few sites,
and every site have around 150-170 access switches.

Requirements:
- 4 * 48 linecards, 10GE SFP+ ports
- Routing: BGP + ISIS
- 12 x 100G ports for inter-site connectivity
- MACsec on 10G and 100G
- Interconnection between sites: Pure-L3, but would like to have ability to
extend L2 VLANs between sites (using EVPN or MPLS)

I considered few platforms:
- Catalyst 9600
- Nexus 9500
- NCS 5508

NCS a bit too expensive. Probably will go for Catalyst or Nexus.
In terms of reliability which solution should I use ?

Is Stack-Wise Virtual similar to VSS which we had on 6500/6800 ?
Can I have different software version on each core/aggregation device ?
(this can provide uninterrupted upgrade with mLAG)

Rob