Vindicator, definitely. You have the Clint. You don’t need another mobile sniper with even worse armor and firepower. And you’ve lost your brawler. The Vindicator is more trooper, but it can sorta substitute for the Wolverine in the brawler role.
The best way to deal with infantry is to avoid them. They’re usually slow and can be moved around while you go after the real targets.
If infantry cannot be avoided, the second best way to deal with infantry is at a distance. Rain AC/5 shells, large laser shots, LRMs munitions and PPC bolts from beyond the range of infantry weapons. You won’t kill many infantry per shot, but they add up and a platoon can be reduced to ineffectiveness in short order.
If you don’t have space or time and must engage infantry within the range of their weapons, alternate munitions — usually SRMs but also ACs and LRMs — are the best way to reduce infantry rapidly. Even if you’re in range of their weapons, you don’t have to be right on top of them and the infernos, frag, flechette, etc. munitions make quick work of platoons.
And if you absolutely must engage infantry while on top of them, your Vindicator has a Small Laser.
The best upgrade to the Clint is to trade the AC/5 and ammo for a Large Laser and four tons of armor. That should be a Class B refit because it’s replacing one weapon type with another weapon type with fewer critical spaces. This maxes out the Clint’s armor, eliminates the ammo vulnerability, and increases damage for a negligible decrease in range. Now the Clint is a jumpy Wolfhound that can actually punch holes in armor and take some licks. If you like to ride the heat scale and aren’t afraid of less-than-optimal armor, go with a PPC and two tons of armor instead of the Large Laser and four.
On the Quickdraw mods, I’d trade the LRM-10 and its ammo for a second SRM-4 and four more tons of armor instead of the jump jets. That nearly maxes out the armor, reduces ammo vulnerabilities, and focuses the Quickdraw on being a short-range brawler, which works well with its superior speed and jump jets. It basically turns the Quickdraw into the Wolverine-like brawler that paired so successfully with the Rifleman in your earlier games. If you still have two refits left, you can bring the rear-firing lasers forward.
You are probably best applying your refits to the Clint and Quickdraw. But if you want to play with the Rifleman, let us know.