Hi Roger - If I understand correctly you have one of those trigger plates with the bolster/ "ears" on top and the trigger is pinned to the plate. These often result in a heavy pull as the leverage point is low and far from the sear. Sort of like being on a see-saw with someone who is heavier than you and they are a longer way from the pivot.
I am not sure if it will work for yours, but you might be able to fit a new trigger to your plate and pin it closer to the sear for more leverage. (Although you might have already considered all this and ruled it out already). If so you don't have to move the whole assembly - keep your plate and you can get a casting of a trigger with a lot of height (metal) on it to work with (get one without a plate), or cold forge your own from mild steel. Take your plate out, remove the old trigger, and fit your new trigger to the slot. Then shape and inlet your new trigger for a higher pivot point, closer to the sear, and pin it in the wood. Hershel shows how to forge a trigger and use this method in his video. I built an English fowler this way and it had a wonderful easy pull.
You will want it to allow a slight bit of play in all positions (full cock, half cock and rest). Make sure you check all 3 because some locks (the L&R Queen Anne for one) have the sear sticking out (down) farther at half cock than the other positions and if there is not at a hair of play at each position the trigger is pressing against the sear and it may not allow the sear to fully engage the notch, which is a safety concern. I.e. Many people will shave the trigger just enough to allow it to engage the full cock notch with no play, which makes it not fully engage the half cock on some locks.
Good luck
Guy