If you want to give him a tough list to play with I'd avoid Assault Marines, Drop Pods and Tacticals to be honest. Kinda sad as such units used to be the core of any Marine list, but that's how things are currently.
I agree on the netlist mentality though. I mean I know what's popular and why it is so I can give proper advice on forums but myself I often use units that aren't considered competetive as well since my groups game evenings are literally beer&pretzels (well not pretzels, but lots of beer and whiskey lol).
The Chaincannon thing is really annoying, yeah. Luckily the Heavy Bolters and Autocannons are very similar bitz so you only have to source the barrels from somewhere and then replace those.
Definitely go Thunderhammer if you want the Lord to deal damage. The weapon is so much better than any other weapon (relics excluded) it's ridiculous. High strength, high AP and flat 3 damage is gold on a character with good WS and lots of attacks.
I don't quite remember, do you play EC or just generally Slaanesh?
If your army isn't EC exclusive you could give the Flawless Host a try for a REALLY mean Daemon Prince as well. As warlord with the Flawless Host warlord trait, Prescience, Talons and Intoxicating Elixir he has 8 S8 AP-2 D2 attacks which generate 4(!) additional attacks on a 5+ against the Blood Angels (1 from the Flawless Host trait which gets boosted to 3 from the warlord trait and 1 from DttFE). With 8 attacks and re-rolling 1s that should be 4-8 additional attacks, so 12-16 attacks with S8 AP-2 D2 in total.
Maybe that's a bit much in such a game though, I got carried away.
Tbh I was thinking of painting up any new CSM's I get as Flawless Host, that way I avoid the scale creep between the old and new stuff and everything looks right. I might try out the Flawless Host using what I have at the moment so I can see what works best for them, then I can purchase units I need not ones I want.
That Flawless Host DP does look tempting, what units would synergise well with him using 'FH' instead of 'EC' rules?
That means Ill end up with Emperors Children (eventually when they drop), Flawless Host, Hellbound (renegades), Hellborn (Daemons), Hella annoying (Traitor Guard), and Pre Heresy Emperors Children. I can almost taste the decadence in the air!!!