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For you current topology (as shown), HSRP wouldn't be useful.
However, as you note you have backup routers and L3 switches, then you might use them with HSRP.
So, for example, if you had another L3 switch, you could connect it to the existing L3 switch and to each L2 switch. Then you could share a virtual gateway IP between the two L3 switches. If the primary gateway device failed the secondary would take over so you wouldn't lose routing between subnets just because the one L3 switched failed.
You could also use HSRP between your L3 switch(es) and your WAN router(s), but as all are L3, normally you would deal with path failure using a routing protocol, not a FHRP (such as HSRP).
