I think your wrong that Fellaini HAS to go due to us needing the money for squad depth. I would imagine we have around 15M to play with, Could even be more when you look at what the likes of Norwich and co are throwing around already! Also remember a lot of deals are done on tick these days.....
There is simply no evidence to suggest that we have £15m ready to spend. You've plucked that figure out of thin air. And if we want to climb the table, or seriously try for a cup, we need a bigger squad with more quality competing for the starting spot at more positions. We are paper-thin on the wings and at CM/DCM; much of the depth at ACM is questionable (Osman's age, Barkley's inexperience, Naismith's quality); the only position where we have real depth is striker!
As for the idea that we must have more to spend because the likes of Norwich do - I fail to see the link between the cashflows of two totally seperate businesses. Do Norwich bung us a few hundred grand every so often?
Goalkeepers - Only got Howard so yes one is needed. That could be a free, loan or indeed cash spent. But you have options which way to go this summer.
COST - £0 - Upwards.
That barely counts as an opinion - you've simply listed every possible approach that can be taken.
Defense - IMO we need to move heitinga on and replace with the money his transfer brings in (roughly 3M) you may have to add a million or 2 out of the kitty but there are also potential free deals to be had.
COST £0 - 3M.
Happy with Alcaraz then? Who else do you see in that price bracket? Climb down off the fence in your own time. Vermaelen would be at least £5m, as would Lescott. Who do you see us bringing in at a lower price?
Midfield - As it stands centeraly inc the No.10 role we have Gibson, Fellaini, Osman, Barkley. I personaly think we only need to bring one money signing into that. A (Fer or Honda) at around 5M would complement them well. Of course 1 or 2 more needed around the squad needed to cover for injuries but free's/loans even (lundstrum) could easily bulk that up.
COST £5 - 8M.
It's fair to say that our reserves (Lundstram et al) aren't ready yet; no-one wants to see Osman in CM again, do they? Gibbo is having an operation over the summer, will he be ready to go come August 17th? Barkley could use another loan out (although he is arguably ready to start for us now), bringing in Honda for £5m would actually aid Barkley's development by facilitating such a loan; We used Neville and Hitz at times in CM/DCM last year - we need to replace them, preferably with better-standard players.
Wingers - Deffinately short here, only really Miralass and pienaar. Could bring in a few Million from Naismith so with free's (Donovan) we could potentially add another couple of squad wingers for a another couple of mill from the kitty.
COST £0 - 3M.
A couple of squad wingers for a combined total of £3m will not bring in ANYONE capable of competing for a starting spot. You'd just be buying more Kennedys. And how much do you REALLY think we'd get from selling Naismith?
Strikers - 100% need to buy one. Dependent on what's done with winger additions we could sell jelavic and add 5M or so from the kitty and buy a 10-12M striker, still having super sub vic and wingers in mirallas and Donovan who can play up front also.
COST £5M - 10M.
The one area we already have depth, and you want to spend £10m on a new player. Give me a name of someone you think we can get in that price range, and I'll show you someone who is no better than an on-form Jelavic. Remember Spurs, Arsenal, WBA, Newcastle, Swansea and City are shopping for strikers too.
General point being we could add what is required without having to sell the big man and be a stronger team/squad. If he wants to go then not much we can do but a few savvy transfer dealings in and out could make a real difference.
I think I've comprehensively demonstrated the flaws in your argument, seeing as it was all based on the fiction of an pre-existing transfer fund of £15m, to be swelled by the sale of Jelavic, Naismith and Heitinga. How much do you see those three going for, £10m? £12m? That's the exact sum you wanted to spend on a striker, so that leaves your original £15m to bolster defence, midfield and the wings. And remember that you made up the £15m to start with.
To progress we need the quality of our squad to improve over more than just the 11 on the pitch - the way to do this is to buy BETTER players than we have already, moving some of our existing starters on to the bench, and this costs money. Selling Fellaini is the most appropriate way to raise the necessary funds because it raises the most money and reduces the squad (in terms of total numbers) the least.