Reports on Tuesday claimed replays could be shelved to help ease fixture congestion
Sky Bet League One Town host Manchester United at Greenhous Meadow on Monday aiming to pull off a huge fifth-round shock
Last season, Cambridge expected to net around Â£1.5million from their televised fourth-round replay at Old Trafford, which they lost 3-0.
Mellon is not thinking about any return tie against United yet as he eyes an upset in Shropshire but insisted lower league sides need the cash boost a replay brings.
"We could lose clubs
Replays keep clubs afloat
I don't know many clubs at this level making money," he said.
"We wash our own face and teeter on and make sure we're not in any debt
To get that extra money in will only help us improve our football club.
"That (taking away replays) would kill us
That's the dream for anybody at this level
To go and play and prove you can function at those levels.
"If you give us less of a chance of doing that it takes a massive part of the romance out of the cup
I want this to be what it is, it's a massive day for us.
"We're not over-awed by it
We're really determined we'll go and enjoy it and get heavily involved in it.
"If you take away that chance of playing at those big stadiums English football loses a massive thing."
The possibility of midweek FA Cup fixtures has also been claimed, while in January FA chief executive Martin Glenn refused to rule out change but insisted they must ensure lower league clubs do not end up out of pocket while also sticking to the competition's principles
Any future decision must be right for all parties and no motion is on the table, with nothing imminent, while the FA remain determined to protect the integrity of the competition
Source : PA