This was a question I first asked on stack exchange, [here](https://math.stackexchange.com/questions/3277807/replacing-the-fibre-of-a-fibration). In my head it seems like a fairly reasonable thing to ask for, but I'm not aware of any construction in the literature.


Let $p:E\rightarrow X$ be a Serre fibration over a pointed, connected CW complex $X$ with strict fibre a CW complex $F=p^{-1}(\ast)$. Given another space $F'$ and a homotopy equivalence $F\simeq F'$, is it possible to construct a Serre fibration $p':E'\rightarrow X$ with strict fibre $F'=p'^{-1}(\ast)$? If $E'$ exists, is it then possible to extend the homotopy equivalence $F\simeq F'$ to a fibre homotopy equivalence $E\simeq E'$ over $X$?


If you assume some extra structure on the fibration $p$ and the homotopy equivalence $F\simeq F'$ then things work out fairly easily, but I'm interested in the more general case.


Really I would like both questions to be taken together, since as pointed out in the comments, the projection $X\times F'\rightarrow X$ trivially satisfies the requirements of the first question alone, and such an answer is not exactly what I was looking for.



Replacing the Fibre of a Fibration
You can make the construction as follows. There are three steps. 


First make a Serre fibration over the unit interval, pi:T->I=[0,1] such that the fibre over 0 (resp. 1) is F (resp. F'). You will find how to make this in the general case; for example, for F=1 point and F'=the interval, here is a proof that the triangle does it. 


Consider in the plane the triangle T: 0<=y<=x<=1 and the projection pi(x,y)=x. Given a CW-complex A, a continuous map from A to T:a->(x\_0(a),y\_0(a)) and a homotopy (x\_t(a)) (0<=t<=1), consider K={(a,t)\in AxI/x\_t(a)=0} and K\_0=(Ax0)\cap K. On the complement (Ax0)\K\_0 you have the slope function s\_0(a):=y\_0(a)/x\_0(a); extend it to a continuous function s from (AxI)\K to I; the wanted homotopy is (a,t)->(x\_t(a),s(a,t)x\_t(a)) for (a,t)\notin K and (a,t)->(0,0) for (a,t)\in K. Hence, pi is a Serre fibration.


Second, let $f:X\rightarrow X$ be homotopic to the identity and contract some
neighborhood $N$ of $\*$ onto $\*$. Pulling back your fibration $p$ through $f$, you are reduced to the case where $p$ is a projection $F\times N\rightarrow N$ over $N$.


Third, consider a function $g: N\rightarrow I$ whose value is $0$ on $\partial N$ and $1$ on $\*$; define $E'$ over $N$
as the amalgamated product of $T$ with $N$ over $pi$ and $g$; define $E'$ as $E$ over $(X-N)$. If you have chosen $N$ to retract by deformation on $\*$, then this $E'$ will have the property you want.


Maybe there is a more elegant way to present the construction (i'm not an expert in homotopy theory nor cw-complexes)


