i know a fix for it!
U force the speed on_tick
making it incompatible (screwing)with my mod, and any other mods that alter speed, or add/removes bonuses..

instead of forcing every tick,(no need, unless users choice) use this:
player.force.manual_crafting_speed_modifier= X
where X equals the amount the user has chosen on settings.lua, only set this ONCE, not on tick....

the code above is inside(under) script.on_event(defines.events.on_player_driving_changed_state, )
so it's like this

script.on_event(defines.events.on_player_driving_changed_state, )
blablabla
player.force.manual_crafting_speed_modifier= X
blablabla

i do that while i enter the workshop(it's a vehicle/type)
and i remove when i quit it

if u need any further help, just ask!

OR, an option[default as FALSE] to FORCE a FIXED crafting speed, never less, never more than users chosen one

btw, mod name is Workbench, Still in progress tho