Team Advice

To utilize that you need a crit star generator. Someone who created those crit stars and frankly Hans isn't good for that. Everyone says that Hans is good for crit teams, but he wouldn't function and do his job fully which is increasing crit damage if there's no crit star gen.
Well you could do this with Merlin, but Hans? No 9 crit stars for 3 turns. A 2030 could easily do that through all the turns and his skill that gives crit stars give only 9 at level 10 and even decreaces his defense.
If you want to do that just use a crit star generator, produce crit stars, change to Hans when Lalter is going to crit and increase her crit damage more.
Do you have the battle suit? If so I recommend getting it since this wouldn't work. Hans will die by a stray crit or if the RNG makes enemies so I suggest putting Hans on your back line and getting a crit star gen to put in your front line and Lalter would just do her job with crit star gather and crit damage increase with added stars.

Swap best kouhai for an assassin to star gen. Hans' NP provides an overlap with some of the benefits mash provides other than her ability to taunt. Cheap assassins with decent star gen include: cursed arm Hassan (poor damage output but good star gen), fuuma koutaro (great star gen, aoe np), welfare plot shishou (the current event's welfare servant who is basically a better version of fuuma).
You can afford to swap out mash because Lancers are fairly durable to begin with and Hans' np covers enough of her support abilities. Alternately friend someone with a Jack the ripper support and swim in all the stars you'll be collecting \o/

Swap out mash for leondias. He provides a taunt stars and a buster buff, all things lancer artoria wants.