its basically what the Skull on LSM side does , so this isn't that brutal.
i think its best to look for fixes for Mot in wargear not the mark
just like how mok gets a weapon with 300 lp's worth of extra LL to make it viable i think we should start looking into wargear for the Mot to do the same, make it viable .

think of a MC force sword with + 300 Lp worth of armor for 300 LP total cost just like the chain axe of khorne has 400 Lp worth of stats on a 200 LP weapon yet only costs you 300 Lp to equip essentially giving you 400 Lp worth of LL for the costs of a 10% LL mod.

for Mot traitors there should be a long ranged weapon variant of the bolter since mot is really well suited for similar roles as the stalker bolter or long barrel bolter classes both of which are not accessible to chaos.