Albion have under a week to add to a small group where, particularly in some positions, options are thin on the ground beyond the regular starters.
Bruce feels his overhaul of the Baggies squad he inherited from Valerien Ismael in February, which he has trimmed significantly, will take longer than one transfer window to complete.
With less than seven days of summer business remaining Albion still want a new striker at The Hawthorns and the manager still sees his squad 'a couple short'. He is happy to work with a squad closer to 20 senior players, as opposed to 28.
Asked about striking a balance with squad depth, Bruce revealed: "It's crucial. I think, and I was open enough with you at the end of last season to say that the squad needed a bit of an overhaul.
"I've let eight go, and we've brought in three. I still think that we're at least a couple short of where we need to be, but I'd rather work with 20 than 28. I've always said that it's not going to happen in one transfer window, not with the restricted finances that we've got.
"It's going to probably take another two or three windows, now whether I can see that through, that's the aim and that's the best way for the club going forward.
"I'm taking a gamble, because we're a little bit short, but I'd rather take the gamble because the club in the long run will be better.
"Otherwise we're just hoarding 28 players and we're not getting the right ones that need to take us forward."
Albion currently have 16 fit and available senior outfield players given injuries to Kenneth Zohore and Kean Bryan.
They let senior players Sam Johnstone, Romaine Sawyers and Andy Carroll depart, as well as loan exits for Cedric Kipre and Alex Mowatt.
Youngsters Zac Ashworth, Ethan Ingram and Reyes Cleary have been involved in cup action but are yet to feature in Bruce's Championship plans.
Albion squad contains three natural senior centre-halves, first-choice pairing Dara O'Shea and Semi Ajayi as well as Kyle Bartley.
Having allowed Alex Mowatt depart on loan for league rivals Middlesbrough, the natural central midfield options consist of Okay Yokuslu, Jayson Molumby and Jake Livermore.
Bruce wants at least another couple of additions before the deadline in what he sees as a 'free-for-all' final week.