TL;DR - Buff marauders as per OP, and give a damage boost through possibly a T2 bastion module.
If I was on the fence before on a damage buff, I may be over the fence now.
https://forums-archive.eveonline.com/default.aspx?g=posts&t=273500&find=unread
The above thread was created by CCP Ytterbium when the previous marauder update in 2013 was being discussed. I was away at the time, but some of you may remember it.
He states that the update was indeed intended to help bridge the gap between battleships and capitals. In light of events of the last 4 years tho, I would disagree of the devs intent on comparing marauders to pirate BS’s. I personally think pirate BS’s should be compared to buffed navy BS’s as per this thread:
According to Eve wiki, marauders are a 115 day train, dreadnoughts are 106 day train, and pirate BS’s are a 6 day train. Pirate BS’s should not be in the same league as marauders. Sorry pirate BS fans. Marauders current prices encroach upon the cost of a capital, and has a longer train time than dreads, but marauders are to capitals as T2 frigs are to battleships. The gap between marauder and capital would maybe require 2-3 new ship classes to fill it. Something which the devs seem to have little interest in creating at this time.
So since the devs already opened the Pandora’s box by creating bastion and turning marauders into basically mini-dreads, it may be about time to look into how marauders can fill out that role more.
After doing a bit more math, a well blinged marauder could possibly tank two other marauders. A 50% increase in damage output may not be out of line. I dare say maybe 100% could be in order as well considering dreads get a 700-800% boost. Perhaps if the damage was added to only T2 version of bastion, maybe give the T2 restrictions that it can’t be used in high sec.
Also, the devs really did take the community’s input into account in the previous update. So if anyone else feels that a marauder buff should be investigated, it would be good to add your arguments to the case. The devs were going to buff fitting stats at first. And then due to community pressure, decided to remove tanking buff. Then after more pressure, reinstated tanking buff. Then finally remove fitting buff, but boost hit point stats, as example.
The devs also took the entire laundry list of changes and implemented them in one pass. So if anyone has a reasonable wish list to add, it would be best to have it all in one go… 
