In a situation like this, I would seriously consider the viability of tanking on the Homeworld itself. If the incoming wormhole layout is favorable, that is. CPAs and Exowaves would require a more forward defense, killing off (or slowing down, at least) the groups to prevent attacks en-masse, but it can be done.
If you have the Zenith Trader on, consider the Black Hole Generator.
Last, but not least, consider a new map.
I've never tried it, but I thought I read somewhere once if you gate raided further (two systems back) in all the direction you didn't want an Exo to come from, you could actually funnel the Exo through a specific Warp Gate. The theory being it won't select a Warp Gate for an Exo is another Warp Gate exists that is closer to the target in terms of hops, but it will randomly select from all equally close Warp Gates. Split Exos might still cause you a problem. And of course maybe I'm mis-remembering.
Exowave battlegroups spawn from Warp Gates, and gate-raiding will prevent them from spawning in those systems. However, I know battlegroups can spawn from at least as far away as three systems. I'm not sure, but it kind of looks like each battlegroup also tries to spawn from a different warp gate.
I think, to be safe, you'd need to gate raid everything north and east of Mardia and Kathwallace.
That would force Exos and CPAs into certain paths. From the northwest (the Red AI's HW brach), they'll likely funnel through Imrik.
From the southwest, it all depends on pathing. If the AI pathing chooses Vulputate to Imrik, you'd be good. But if it says Vulputate to REM Z21-63, you're out of luck.
From the south and southeast, everything would go through Flandern, Mardia, and Kathwallace. Flandern wouldn't be as much of a concern to defend, though, because neither Oort nor Metcalf would be a source of ships.
Unfortunately, that's still 4 systems, minimum, to defend, and 8 to gate-raid. It also requires a good amount of forward action to keep the threatfleet from concentrating.
That means that each CPA would need to be handled first using the mobile fleet, preferably before it relocates into carriers.
As for me, I might try this against diff 9 AI. I wouldn't against a diff 10, though. More likely, I'd just try to see if I could over-fortify my Homeworld and pray for luck. If the Homeworld wormhole layout was bad enough, I'd just start a new game.