i basically use my tuffli as a bank. currently i have a regular reman set on it, which i will never upgrade (already having done that once.....not again).
i had extra tetryon mk 12 beams i put on it and in the devices i just store extra stuff i have. right now i have it loaded up with turrets fabricated from alien devices.
i just see this ship as a convenient way to bank, , access the exchange, switch ships, pick up low priced commodities, etc.
my wife does assignments for me during the day and she likes it because she can easily warp around in it to find me good assignments.
one time i forgot to change ships while in the tuffli and entered a fleet base defense while in it. i looked pretty silly. at least i had heals so i was able to stay close to the base and heal it, but basically i was easy prey in there.
you can easily go back and forth between the tuffli and other ships limiting the amount of time you spend going to a base for banking and such.
Roughly translated: The tuffli makes it so you never have to visit ESD or DS9. Unless you need to sell things in which case you do need to visit, but other than that, it's basically the widdle fweighter that could. BTW, as rdm stated, don't get into a fight with it. 1st, you look silly. 2nd, you die lots. 3rd, well I think the first two are more than enough reason don't you?
I have found myself in combat in the freighter i'm certain it was a regulas sector borg invasion. and to be honest other than feeling really stupid, it actully worked well as a support ship. i had reman X shield, combat impulse IX. also had tractor mines on the back with a plasma torpedo III and a disruptor canon VI. only one team death and that was me when one of those energy orbs got me ( coz speed as u know is poor) but yeah its nice becuse if its low threat gen which allows u to support others with little problems.
I finally got my freighter for $15 worth of keys. I've been a fan of the doff system since its inception, so it works out pretty well for me. So far it has been great for focusing assignments on particular fields. I dubbed my ship the S.S. Heretic =p.
I'm not really sure what to put on the ship for devices, but the transwarp consoles might help lower transwarp cooldowns, as well as a purple transwarp Doff (not sure if they stack or whatnot). STF engines or a fleet engine would work for optimal sector space speeds (I think M.A.C.O. would be the best due to the +driver coil).
If they allow the Tuffli to benefit from the Ferengi Marauder 3 piece set. Then I would definitely put that on. Afterall as the Tuffli description states Ferengi (aswell as some other minor species) designs are the standard for freighters.